TOMOYO Linux Cross Reference
Linux/net/core/skbuff.c

   // SPDX-License-Identifier: GPL-2.0-or-later
   /*
    *      Routines having to do with the 'struct sk_buff' memory handlers.
    *
    *      Authors:        Alan Cox <alan@lxorguk.ukuu.org.uk>
    *                      Florian La Roche <rzsfl@rz.uni-sb.de>
    *
    *      Fixes:
    *              Alan Cox        :       Fixed the worst of the load
   *                                      balancer bugs.
   *              Dave Platt      :       Interrupt stacking fix.
   *      Richard Kooijman        :       Timestamp fixes.
   *              Alan Cox        :       Changed buffer format.
   *              Alan Cox        :       destructor hook for AF_UNIX etc.
   *              Linus Torvalds  :       Better skb_clone.
   *              Alan Cox        :       Added skb_copy.
   *              Alan Cox        :       Added all the changed routines Linus
   *                                      only put in the headers
   *              Ray VanTassle   :       Fixed --skb->lock in free
   *              Alan Cox        :       skb_copy copy arp field
   *              Andi Kleen      :       slabified it.
   *              Robert Olsson   :       Removed skb_head_pool
   *
   *      NOTE:
   *              The __skb_ routines should be called with interrupts
   *      disabled, or you better be *real* sure that the operation is atomic
   *      with respect to whatever list is being frobbed (e.g. via lock_sock()
   *      or via disabling bottom half handlers, etc).
   */
  
  /*
   *      The functions in this file will not compile correctly with gcc 2.4.x
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <linux/in.h>
  #include <linux/inet.h>
  #include <linux/slab.h>
  #include <linux/tcp.h>
  #include <linux/udp.h>
  #include <linux/sctp.h>
  #include <linux/netdevice.h>
  #ifdef CONFIG_NET_CLS_ACT
  #include <net/pkt_sched.h>
  #endif
  #include <linux/string.h>
  #include <linux/skbuff.h>
  #include <linux/skbuff_ref.h>
  #include <linux/splice.h>
  #include <linux/cache.h>
  #include <linux/rtnetlink.h>
  #include <linux/init.h>
  #include <linux/scatterlist.h>
  #include <linux/errqueue.h>
  #include <linux/prefetch.h>
  #include <linux/bitfield.h>
  #include <linux/if_vlan.h>
  #include <linux/mpls.h>
  #include <linux/kcov.h>
  #include <linux/iov_iter.h>
  
  #include <net/protocol.h>
  #include <net/dst.h>
  #include <net/sock.h>
  #include <net/checksum.h>
  #include <net/gso.h>
  #include <net/hotdata.h>
  #include <net/ip6_checksum.h>
  #include <net/xfrm.h>
  #include <net/mpls.h>
  #include <net/mptcp.h>
  #include <net/mctp.h>
  #include <net/page_pool/helpers.h>
  #include <net/dropreason.h>
  
  #include <linux/uaccess.h>
  #include <trace/events/skb.h>
  #include <linux/highmem.h>
  #include <linux/capability.h>
  #include <linux/user_namespace.h>
  #include <linux/indirect_call_wrapper.h>
  #include <linux/textsearch.h>
  
  #include "dev.h"
  #include "sock_destructor.h"
  
  #ifdef CONFIG_SKB_EXTENSIONS
  static struct kmem_cache *skbuff_ext_cache __ro_after_init;
  #endif
  
  #define SKB_SMALL_HEAD_SIZE SKB_HEAD_ALIGN(MAX_TCP_HEADER)
  
  /* We want SKB_SMALL_HEAD_CACHE_SIZE to not be a power of two.
  * This should ensure that SKB_SMALL_HEAD_HEADROOM is a unique
  * size, and we can differentiate heads from skb_small_head_cache
  * vs system slabs by looking at their size (skb_end_offset()).
  */
 #define SKB_SMALL_HEAD_CACHE_SIZE                                       \
         (is_power_of_2(SKB_SMALL_HEAD_SIZE) ?                   \
                 (SKB_SMALL_HEAD_SIZE + L1_CACHE_BYTES) :        \
                 SKB_SMALL_HEAD_SIZE)
 
 #define SKB_SMALL_HEAD_HEADROOM                                         \
         SKB_WITH_OVERHEAD(SKB_SMALL_HEAD_CACHE_SIZE)
 
 /* kcm_write_msgs() relies on casting paged frags to bio_vec to use
  * iov_iter_bvec(). These static asserts ensure the cast is valid is long as the
  * netmem is a page.
  */
 static_assert(offsetof(struct bio_vec, bv_page) ==
               offsetof(skb_frag_t, netmem));
 static_assert(sizeof_field(struct bio_vec, bv_page) ==
               sizeof_field(skb_frag_t, netmem));
 
 static_assert(offsetof(struct bio_vec, bv_len) == offsetof(skb_frag_t, len));
 static_assert(sizeof_field(struct bio_vec, bv_len) ==
               sizeof_field(skb_frag_t, len));
 
 static_assert(offsetof(struct bio_vec, bv_offset) ==
               offsetof(skb_frag_t, offset));
 static_assert(sizeof_field(struct bio_vec, bv_offset) ==
               sizeof_field(skb_frag_t, offset));
 
 #undef FN
 #define FN(reason) [SKB_DROP_REASON_##reason] = #reason,
 static const char * const drop_reasons[] = {
         [SKB_CONSUMED] = "CONSUMED",
         DEFINE_DROP_REASON(FN, FN)
 };
 
 static const struct drop_reason_list drop_reasons_core = {
         .reasons = drop_reasons,
         .n_reasons = ARRAY_SIZE(drop_reasons),
 };
 
 const struct drop_reason_list __rcu *
 drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM] = {
         [SKB_DROP_REASON_SUBSYS_CORE] = RCU_INITIALIZER(&drop_reasons_core),
 };
 EXPORT_SYMBOL(drop_reasons_by_subsys);
 
 /**
  * drop_reasons_register_subsys - register another drop reason subsystem
  * @subsys: the subsystem to register, must not be the core
  * @list: the list of drop reasons within the subsystem, must point to
  *      a statically initialized list
  */
 void drop_reasons_register_subsys(enum skb_drop_reason_subsys subsys,
                                   const struct drop_reason_list *list)
 {
         if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE ||
                  subsys >= ARRAY_SIZE(drop_reasons_by_subsys),
                  "invalid subsystem %d\n", subsys))
                 return;
 
         /* must point to statically allocated memory, so INIT is OK */
         RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], list);
 }
 EXPORT_SYMBOL_GPL(drop_reasons_register_subsys);
 
 /**
  * drop_reasons_unregister_subsys - unregister a drop reason subsystem
  * @subsys: the subsystem to remove, must not be the core
  *
  * Note: This will synchronize_rcu() to ensure no users when it returns.
  */
 void drop_reasons_unregister_subsys(enum skb_drop_reason_subsys subsys)
 {
         if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE ||
                  subsys >= ARRAY_SIZE(drop_reasons_by_subsys),
                  "invalid subsystem %d\n", subsys))
                 return;
 
         RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], NULL);
 
         synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(drop_reasons_unregister_subsys);
 
 /**
  *      skb_panic - private function for out-of-line support
  *      @skb:   buffer
  *      @sz:    size
  *      @addr:  address
  *      @msg:   skb_over_panic or skb_under_panic
  *
  *      Out-of-line support for skb_put() and skb_push().
  *      Called via the wrapper skb_over_panic() or skb_under_panic().
  *      Keep out of line to prevent kernel bloat.
  *      __builtin_return_address is not used because it is not always reliable.
  */
 static void skb_panic(struct sk_buff *skb, unsigned int sz, void *addr,
                       const char msg[])
 {
         pr_emerg("%s: text:%px len:%d put:%d head:%px data:%px tail:%#lx end:%#lx dev:%s\n",
                  msg, addr, skb->len, sz, skb->head, skb->data,
                  (unsigned long)skb->tail, (unsigned long)skb->end,
                  skb->dev ? skb->dev->name : "<NULL>");
         BUG();
 }
 
 static void skb_over_panic(struct sk_buff *skb, unsigned int sz, void *addr)
 {
         skb_panic(skb, sz, addr, __func__);
 }
 
 static void skb_under_panic(struct sk_buff *skb, unsigned int sz, void *addr)
 {
         skb_panic(skb, sz, addr, __func__);
 }
 
 #define NAPI_SKB_CACHE_SIZE     64
 #define NAPI_SKB_CACHE_BULK     16
 #define NAPI_SKB_CACHE_HALF     (NAPI_SKB_CACHE_SIZE / 2)
 
 #if PAGE_SIZE == SZ_4K
 
 #define NAPI_HAS_SMALL_PAGE_FRAG        1
 #define NAPI_SMALL_PAGE_PFMEMALLOC(nc)  ((nc).pfmemalloc)
 
 /* specialized page frag allocator using a single order 0 page
  * and slicing it into 1K sized fragment. Constrained to systems
  * with a very limited amount of 1K fragments fitting a single
  * page - to avoid excessive truesize underestimation
  */
 
 struct page_frag_1k {
         void *va;
         u16 offset;
         bool pfmemalloc;
 };
 
 static void *page_frag_alloc_1k(struct page_frag_1k *nc, gfp_t gfp)
 {
         struct page *page;
         int offset;
 
         offset = nc->offset - SZ_1K;
         if (likely(offset >= 0))
                 goto use_frag;
 
         page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
         if (!page)
                 return NULL;
 
         nc->va = page_address(page);
         nc->pfmemalloc = page_is_pfmemalloc(page);
         offset = PAGE_SIZE - SZ_1K;
         page_ref_add(page, offset / SZ_1K);
 
 use_frag:
         nc->offset = offset;
         return nc->va + offset;
 }
 #else
 
 /* the small page is actually unused in this build; add dummy helpers
  * to please the compiler and avoid later preprocessor's conditionals
  */
 #define NAPI_HAS_SMALL_PAGE_FRAG        0
 #define NAPI_SMALL_PAGE_PFMEMALLOC(nc)  false
 
 struct page_frag_1k {
 };
 
 static void *page_frag_alloc_1k(struct page_frag_1k *nc, gfp_t gfp_mask)
 {
         return NULL;
 }
 
 #endif
 
 struct napi_alloc_cache {
         local_lock_t bh_lock;
         struct page_frag_cache page;
         struct page_frag_1k page_small;
         unsigned int skb_count;
         void *skb_cache[NAPI_SKB_CACHE_SIZE];
 };
 
 static DEFINE_PER_CPU(struct page_frag_cache, netdev_alloc_cache);
 static DEFINE_PER_CPU(struct napi_alloc_cache, napi_alloc_cache) = {
         .bh_lock = INIT_LOCAL_LOCK(bh_lock),
 };
 
 /* Double check that napi_get_frags() allocates skbs with
  * skb->head being backed by slab, not a page fragment.
  * This is to make sure bug fixed in 3226b158e67c
  * ("net: avoid 32 x truesize under-estimation for tiny skbs")
  * does not accidentally come back.
  */
 void napi_get_frags_check(struct napi_struct *napi)
 {
         struct sk_buff *skb;
 
         local_bh_disable();
         skb = napi_get_frags(napi);
         WARN_ON_ONCE(!NAPI_HAS_SMALL_PAGE_FRAG && skb && skb->head_frag);
         napi_free_frags(napi);
         local_bh_enable();
 }
 
 void *__napi_alloc_frag_align(unsigned int fragsz, unsigned int align_mask)
 {
         struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
         void *data;
 
         fragsz = SKB_DATA_ALIGN(fragsz);
 
         local_lock_nested_bh(&napi_alloc_cache.bh_lock);
         data = __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC,
                                        align_mask);
         local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
         return data;
 
 }
 EXPORT_SYMBOL(__napi_alloc_frag_align);
 
 void *__netdev_alloc_frag_align(unsigned int fragsz, unsigned int align_mask)
 {
         void *data;
 
         if (in_hardirq() || irqs_disabled()) {
                 struct page_frag_cache *nc = this_cpu_ptr(&netdev_alloc_cache);
 
                 fragsz = SKB_DATA_ALIGN(fragsz);
                 data = __page_frag_alloc_align(nc, fragsz, GFP_ATOMIC,
                                                align_mask);
         } else {
                 local_bh_disable();
                 data = __napi_alloc_frag_align(fragsz, align_mask);
                 local_bh_enable();
         }
         return data;
 }
 EXPORT_SYMBOL(__netdev_alloc_frag_align);
 
 static struct sk_buff *napi_skb_cache_get(void)
 {
         struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
         struct sk_buff *skb;
 
         local_lock_nested_bh(&napi_alloc_cache.bh_lock);
         if (unlikely(!nc->skb_count)) {
                 nc->skb_count = kmem_cache_alloc_bulk(net_hotdata.skbuff_cache,
                                                       GFP_ATOMIC,
                                                       NAPI_SKB_CACHE_BULK,
                                                       nc->skb_cache);
                 if (unlikely(!nc->skb_count)) {
                         local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
                         return NULL;
                 }
         }
 
         skb = nc->skb_cache[--nc->skb_count];
         local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
         kasan_mempool_unpoison_object(skb, kmem_cache_size(net_hotdata.skbuff_cache));
 
         return skb;
 }
 
 static inline void __finalize_skb_around(struct sk_buff *skb, void *data,
                                          unsigned int size)
 {
         struct skb_shared_info *shinfo;
 
         size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
         /* Assumes caller memset cleared SKB */
         skb->truesize = SKB_TRUESIZE(size);
         refcount_set(&skb->users, 1);
         skb->head = data;
         skb->data = data;
         skb_reset_tail_pointer(skb);
         skb_set_end_offset(skb, size);
         skb->mac_header = (typeof(skb->mac_header))~0U;
         skb->transport_header = (typeof(skb->transport_header))~0U;
         skb->alloc_cpu = raw_smp_processor_id();
         /* make sure we initialize shinfo sequentially */
         shinfo = skb_shinfo(skb);
         memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
         atomic_set(&shinfo->dataref, 1);
 
         skb_set_kcov_handle(skb, kcov_common_handle());
 }
 
 static inline void *__slab_build_skb(struct sk_buff *skb, void *data,
                                      unsigned int *size)
 {
         void *resized;
 
         /* Must find the allocation size (and grow it to match). */
         *size = ksize(data);
         /* krealloc() will immediately return "data" when
          * "ksize(data)" is requested: it is the existing upper
          * bounds. As a result, GFP_ATOMIC will be ignored. Note
          * that this "new" pointer needs to be passed back to the
          * caller for use so the __alloc_size hinting will be
          * tracked correctly.
          */
         resized = krealloc(data, *size, GFP_ATOMIC);
         WARN_ON_ONCE(resized != data);
         return resized;
 }
 
 /* build_skb() variant which can operate on slab buffers.
  * Note that this should be used sparingly as slab buffers
  * cannot be combined efficiently by GRO!
  */
 struct sk_buff *slab_build_skb(void *data)
 {
         struct sk_buff *skb;
         unsigned int size;
 
         skb = kmem_cache_alloc(net_hotdata.skbuff_cache, GFP_ATOMIC);
         if (unlikely(!skb))
                 return NULL;
 
         memset(skb, 0, offsetof(struct sk_buff, tail));
         data = __slab_build_skb(skb, data, &size);
         __finalize_skb_around(skb, data, size);
 
         return skb;
 }
 EXPORT_SYMBOL(slab_build_skb);
 
 /* Caller must provide SKB that is memset cleared */
 static void __build_skb_around(struct sk_buff *skb, void *data,
                                unsigned int frag_size)
 {
         unsigned int size = frag_size;
 
         /* frag_size == 0 is considered deprecated now. Callers
          * using slab buffer should use slab_build_skb() instead.
          */
         if (WARN_ONCE(size == 0, "Use slab_build_skb() instead"))
                 data = __slab_build_skb(skb, data, &size);
 
         __finalize_skb_around(skb, data, size);
 }
 
 /**
  * __build_skb - build a network buffer
  * @data: data buffer provided by caller
  * @frag_size: size of data (must not be 0)
  *
  * Allocate a new &sk_buff. Caller provides space holding head and
  * skb_shared_info. @data must have been allocated from the page
  * allocator or vmalloc(). (A @frag_size of 0 to indicate a kmalloc()
  * allocation is deprecated, and callers should use slab_build_skb()
  * instead.)
  * The return is the new skb buffer.
  * On a failure the return is %NULL, and @data is not freed.
  * Notes :
  *  Before IO, driver allocates only data buffer where NIC put incoming frame
  *  Driver should add room at head (NET_SKB_PAD) and
  *  MUST add room at tail (SKB_DATA_ALIGN(skb_shared_info))
  *  After IO, driver calls build_skb(), to allocate sk_buff and populate it
  *  before giving packet to stack.
  *  RX rings only contains data buffers, not full skbs.
  */
 struct sk_buff *__build_skb(void *data, unsigned int frag_size)
 {
         struct sk_buff *skb;
 
         skb = kmem_cache_alloc(net_hotdata.skbuff_cache, GFP_ATOMIC);
         if (unlikely(!skb))
                 return NULL;
 
         memset(skb, 0, offsetof(struct sk_buff, tail));
         __build_skb_around(skb, data, frag_size);
 
         return skb;
 }
 
 /* build_skb() is wrapper over __build_skb(), that specifically
  * takes care of skb->head and skb->pfmemalloc
  */
 struct sk_buff *build_skb(void *data, unsigned int frag_size)
 {
         struct sk_buff *skb = __build_skb(data, frag_size);
 
         if (likely(skb && frag_size)) {
                 skb->head_frag = 1;
                 skb_propagate_pfmemalloc(virt_to_head_page(data), skb);
         }
         return skb;
 }
 EXPORT_SYMBOL(build_skb);
 
 /**
  * build_skb_around - build a network buffer around provided skb
  * @skb: sk_buff provide by caller, must be memset cleared
  * @data: data buffer provided by caller
  * @frag_size: size of data
  */
 struct sk_buff *build_skb_around(struct sk_buff *skb,
                                  void *data, unsigned int frag_size)
 {
         if (unlikely(!skb))
                 return NULL;
 
         __build_skb_around(skb, data, frag_size);
 
         if (frag_size) {
                 skb->head_frag = 1;
                 skb_propagate_pfmemalloc(virt_to_head_page(data), skb);
         }
         return skb;
 }
 EXPORT_SYMBOL(build_skb_around);
 
 /**
  * __napi_build_skb - build a network buffer
  * @data: data buffer provided by caller
  * @frag_size: size of data
  *
  * Version of __build_skb() that uses NAPI percpu caches to obtain
  * skbuff_head instead of inplace allocation.
  *
  * Returns a new &sk_buff on success, %NULL on allocation failure.
  */
 static struct sk_buff *__napi_build_skb(void *data, unsigned int frag_size)
 {
         struct sk_buff *skb;
 
         skb = napi_skb_cache_get();
         if (unlikely(!skb))
                 return NULL;
 
         memset(skb, 0, offsetof(struct sk_buff, tail));
         __build_skb_around(skb, data, frag_size);
 
         return skb;
 }
 
 /**
  * napi_build_skb - build a network buffer
  * @data: data buffer provided by caller
  * @frag_size: size of data
  *
  * Version of __napi_build_skb() that takes care of skb->head_frag
  * and skb->pfmemalloc when the data is a page or page fragment.
  *
  * Returns a new &sk_buff on success, %NULL on allocation failure.
  */
 struct sk_buff *napi_build_skb(void *data, unsigned int frag_size)
 {
         struct sk_buff *skb = __napi_build_skb(data, frag_size);
 
         if (likely(skb) && frag_size) {
                 skb->head_frag = 1;
                 skb_propagate_pfmemalloc(virt_to_head_page(data), skb);
         }
 
         return skb;
 }
 EXPORT_SYMBOL(napi_build_skb);
 
 /*
  * kmalloc_reserve is a wrapper around kmalloc_node_track_caller that tells
  * the caller if emergency pfmemalloc reserves are being used. If it is and
  * the socket is later found to be SOCK_MEMALLOC then PFMEMALLOC reserves
  * may be used. Otherwise, the packet data may be discarded until enough
  * memory is free
  */
 static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
                              bool *pfmemalloc)
 {
         bool ret_pfmemalloc = false;
         size_t obj_size;
         void *obj;
 
         obj_size = SKB_HEAD_ALIGN(*size);
         if (obj_size <= SKB_SMALL_HEAD_CACHE_SIZE &&
             !(flags & KMALLOC_NOT_NORMAL_BITS)) {
                 obj = kmem_cache_alloc_node(net_hotdata.skb_small_head_cache,
                                 flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
                                 node);
                 *size = SKB_SMALL_HEAD_CACHE_SIZE;
                 if (obj || !(gfp_pfmemalloc_allowed(flags)))
                         goto out;
                 /* Try again but now we are using pfmemalloc reserves */
                 ret_pfmemalloc = true;
                 obj = kmem_cache_alloc_node(net_hotdata.skb_small_head_cache, flags, node);
                 goto out;
         }
 
         obj_size = kmalloc_size_roundup(obj_size);
         /* The following cast might truncate high-order bits of obj_size, this
          * is harmless because kmalloc(obj_size >= 2^32) will fail anyway.
          */
         *size = (unsigned int)obj_size;
 
         /*
          * Try a regular allocation, when that fails and we're not entitled
          * to the reserves, fail.
          */
         obj = kmalloc_node_track_caller(obj_size,
                                         flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
                                         node);
         if (obj || !(gfp_pfmemalloc_allowed(flags)))
                 goto out;
 
         /* Try again but now we are using pfmemalloc reserves */
         ret_pfmemalloc = true;
         obj = kmalloc_node_track_caller(obj_size, flags, node);
 
 out:
         if (pfmemalloc)
                 *pfmemalloc = ret_pfmemalloc;
 
         return obj;
 }
 
 /*      Allocate a new skbuff. We do this ourselves so we can fill in a few
  *      'private' fields and also do memory statistics to find all the
  *      [BEEP] leaks.
  *
  */
 
 /**
  *      __alloc_skb     -       allocate a network buffer
  *      @size: size to allocate
  *      @gfp_mask: allocation mask
  *      @flags: If SKB_ALLOC_FCLONE is set, allocate from fclone cache
  *              instead of head cache and allocate a cloned (child) skb.
  *              If SKB_ALLOC_RX is set, __GFP_MEMALLOC will be used for
  *              allocations in case the data is required for writeback
  *      @node: numa node to allocate memory on
  *
  *      Allocate a new &sk_buff. The returned buffer has no headroom and a
  *      tail room of at least size bytes. The object has a reference count
  *      of one. The return is the buffer. On a failure the return is %NULL.
  *
  *      Buffers may only be allocated from interrupts using a @gfp_mask of
  *      %GFP_ATOMIC.
  */
 struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
                             int flags, int node)
 {
         struct kmem_cache *cache;
         struct sk_buff *skb;
         bool pfmemalloc;
         u8 *data;
 
         cache = (flags & SKB_ALLOC_FCLONE)
                 ? net_hotdata.skbuff_fclone_cache : net_hotdata.skbuff_cache;
 
         if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
                 gfp_mask |= __GFP_MEMALLOC;
 
         /* Get the HEAD */
         if ((flags & (SKB_ALLOC_FCLONE | SKB_ALLOC_NAPI)) == SKB_ALLOC_NAPI &&
             likely(node == NUMA_NO_NODE || node == numa_mem_id()))
                 skb = napi_skb_cache_get();
         else
                 skb = kmem_cache_alloc_node(cache, gfp_mask & ~GFP_DMA, node);
         if (unlikely(!skb))
                 return NULL;
         prefetchw(skb);
 
         /* We do our best to align skb_shared_info on a separate cache
          * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
          * aligned memory blocks, unless SLUB/SLAB debug is enabled.
          * Both skb->head and skb_shared_info are cache line aligned.
          */
         data = kmalloc_reserve(&size, gfp_mask, node, &pfmemalloc);
         if (unlikely(!data))
                 goto nodata;
         /* kmalloc_size_roundup() might give us more room than requested.
          * Put skb_shared_info exactly at the end of allocated zone,
          * to allow max possible filling before reallocation.
          */
         prefetchw(data + SKB_WITH_OVERHEAD(size));
 
         /*
          * Only clear those fields we need to clear, not those that we will
          * actually initialise below. Hence, don't put any more fields after
          * the tail pointer in struct sk_buff!
          */
         memset(skb, 0, offsetof(struct sk_buff, tail));
         __build_skb_around(skb, data, size);
         skb->pfmemalloc = pfmemalloc;
 
         if (flags & SKB_ALLOC_FCLONE) {
                 struct sk_buff_fclones *fclones;
 
                 fclones = container_of(skb, struct sk_buff_fclones, skb1);
 
                 skb->fclone = SKB_FCLONE_ORIG;
                 refcount_set(&fclones->fclone_ref, 1);
         }
 
         return skb;
 
 nodata:
         kmem_cache_free(cache, skb);
         return NULL;
 }
 EXPORT_SYMBOL(__alloc_skb);
 
 /**
  *      __netdev_alloc_skb - allocate an skbuff for rx on a specific device
  *      @dev: network device to receive on
  *      @len: length to allocate
  *      @gfp_mask: get_free_pages mask, passed to alloc_skb
  *
  *      Allocate a new &sk_buff and assign it a usage count of one. The
  *      buffer has NET_SKB_PAD headroom built in. Users should allocate
  *      the headroom they think they need without accounting for the
  *      built in space. The built in space is used for optimisations.
  *
  *      %NULL is returned if there is no free memory.
  */
 struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
                                    gfp_t gfp_mask)
 {
         struct page_frag_cache *nc;
         struct sk_buff *skb;
         bool pfmemalloc;
         void *data;
 
         len += NET_SKB_PAD;
 
         /* If requested length is either too small or too big,
          * we use kmalloc() for skb->head allocation.
          */
         if (len <= SKB_WITH_OVERHEAD(1024) ||
             len > SKB_WITH_OVERHEAD(PAGE_SIZE) ||
             (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) {
                 skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE);
                 if (!skb)
                         goto skb_fail;
                 goto skb_success;
         }
 
         len = SKB_HEAD_ALIGN(len);
 
         if (sk_memalloc_socks())
                 gfp_mask |= __GFP_MEMALLOC;
 
         if (in_hardirq() || irqs_disabled()) {
                 nc = this_cpu_ptr(&netdev_alloc_cache);
                 data = page_frag_alloc(nc, len, gfp_mask);
                 pfmemalloc = nc->pfmemalloc;
         } else {
                 local_bh_disable();
                 local_lock_nested_bh(&napi_alloc_cache.bh_lock);
 
                 nc = this_cpu_ptr(&napi_alloc_cache.page);
                 data = page_frag_alloc(nc, len, gfp_mask);
                 pfmemalloc = nc->pfmemalloc;
 
                 local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
                 local_bh_enable();
         }
 
         if (unlikely(!data))
                 return NULL;
 
         skb = __build_skb(data, len);
         if (unlikely(!skb)) {
                 skb_free_frag(data);
                 return NULL;
         }
 
         if (pfmemalloc)
                 skb->pfmemalloc = 1;
         skb->head_frag = 1;
 
 skb_success:
         skb_reserve(skb, NET_SKB_PAD);
         skb->dev = dev;
 
 skb_fail:
         return skb;
 }
 EXPORT_SYMBOL(__netdev_alloc_skb);
 
 /**
  *      napi_alloc_skb - allocate skbuff for rx in a specific NAPI instance
  *      @napi: napi instance this buffer was allocated for
  *      @len: length to allocate
  *
  *      Allocate a new sk_buff for use in NAPI receive.  This buffer will
  *      attempt to allocate the head from a special reserved region used
  *      only for NAPI Rx allocation.  By doing this we can save several
  *      CPU cycles by avoiding having to disable and re-enable IRQs.
  *
  *      %NULL is returned if there is no free memory.
  */
 struct sk_buff *napi_alloc_skb(struct napi_struct *napi, unsigned int len)
 {
         gfp_t gfp_mask = GFP_ATOMIC | __GFP_NOWARN;
         struct napi_alloc_cache *nc;
         struct sk_buff *skb;
         bool pfmemalloc;
         void *data;
 
         DEBUG_NET_WARN_ON_ONCE(!in_softirq());
         len += NET_SKB_PAD + NET_IP_ALIGN;
 
         /* If requested length is either too small or too big,
          * we use kmalloc() for skb->head allocation.
          * When the small frag allocator is available, prefer it over kmalloc
          * for small fragments
          */
         if ((!NAPI_HAS_SMALL_PAGE_FRAG && len <= SKB_WITH_OVERHEAD(1024)) ||
             len > SKB_WITH_OVERHEAD(PAGE_SIZE) ||
             (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) {
                 skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX | SKB_ALLOC_NAPI,
                                   NUMA_NO_NODE);
                 if (!skb)
                         goto skb_fail;
                 goto skb_success;
         }
 
         if (sk_memalloc_socks())
                 gfp_mask |= __GFP_MEMALLOC;
 
         local_lock_nested_bh(&napi_alloc_cache.bh_lock);
         nc = this_cpu_ptr(&napi_alloc_cache);
         if (NAPI_HAS_SMALL_PAGE_FRAG && len <= SKB_WITH_OVERHEAD(1024)) {
                 /* we are artificially inflating the allocation size, but
                  * that is not as bad as it may look like, as:
                  * - 'len' less than GRO_MAX_HEAD makes little sense
                  * - On most systems, larger 'len' values lead to fragment
                  *   size above 512 bytes
                  * - kmalloc would use the kmalloc-1k slab for such values
                  * - Builds with smaller GRO_MAX_HEAD will very likely do
                  *   little networking, as that implies no WiFi and no
                  *   tunnels support, and 32 bits arches.
                  */
                 len = SZ_1K;
 
                 data = page_frag_alloc_1k(&nc->page_small, gfp_mask);
                 pfmemalloc = NAPI_SMALL_PAGE_PFMEMALLOC(nc->page_small);
         } else {
                 len = SKB_HEAD_ALIGN(len);
 
                 data = page_frag_alloc(&nc->page, len, gfp_mask);
                 pfmemalloc = nc->page.pfmemalloc;
         }
         local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
 
         if (unlikely(!data))
                 return NULL;
 
         skb = __napi_build_skb(data, len);
         if (unlikely(!skb)) {
                 skb_free_frag(data);
                 return NULL;
         }
 
         if (pfmemalloc)
                 skb->pfmemalloc = 1;
         skb->head_frag = 1;
 
 skb_success:
         skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
         skb->dev = napi->dev;
 
 skb_fail:
         return skb;
 }
 EXPORT_SYMBOL(napi_alloc_skb);
 
 void skb_add_rx_frag_netmem(struct sk_buff *skb, int i, netmem_ref netmem,
                             int off, int size, unsigned int truesize)
 {
         DEBUG_NET_WARN_ON_ONCE(size > truesize);
 
         skb_fill_netmem_desc(skb, i, netmem, off, size);
         skb->len += size;
         skb->data_len += size;
         skb->truesize += truesize;
 }
 EXPORT_SYMBOL(skb_add_rx_frag_netmem);
 
 void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
                           unsigned int truesize)
 {
         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
         DEBUG_NET_WARN_ON_ONCE(size > truesize);
 
         skb_frag_size_add(frag, size);
         skb->len += size;
         skb->data_len += size;
         skb->truesize += truesize;
 }
 EXPORT_SYMBOL(skb_coalesce_rx_frag);
 
 static void skb_drop_list(struct sk_buff **listp)
 {
         kfree_skb_list(*listp);
         *listp = NULL;
 }
 
 static inline void skb_drop_fraglist(struct sk_buff *skb)
 {
         skb_drop_list(&skb_shinfo(skb)->frag_list);
 }
 
 static void skb_clone_fraglist(struct sk_buff *skb)
 {
         struct sk_buff *list;
 
         skb_walk_frags(skb, list)
                 skb_get(list);
 }
 
 static bool is_pp_page(struct page *page)
 {
         return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
 }
 
 int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
                     unsigned int headroom)
 {
 #if IS_ENABLED(CONFIG_PAGE_POOL)
         u32 size, truesize, len, max_head_size, off;
         struct sk_buff *skb = *pskb, *nskb;
         int err, i, head_off;
         void *data;
 
         /* XDP does not support fraglist so we need to linearize
          * the skb.
          */
         if (skb_has_frag_list(skb))
                 return -EOPNOTSUPP;
 
         max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE - headroom);
         if (skb->len > max_head_size + MAX_SKB_FRAGS * PAGE_SIZE)
                 return -ENOMEM;
 
         size = min_t(u32, skb->len, max_head_size);
         truesize = SKB_HEAD_ALIGN(size) + headroom;
         data = page_pool_dev_alloc_va(pool, &truesize);
         if (!data)
                 return -ENOMEM;
 
         nskb = napi_build_skb(data, truesize);
         if (!nskb) {
                 page_pool_free_va(pool, data, true);
                 return -ENOMEM;
         }
 
         skb_reserve(nskb, headroom);
         skb_copy_header(nskb, skb);
         skb_mark_for_recycle(nskb);
 
         err = skb_copy_bits(skb, 0, nskb->data, size);
         if (err) {
                 consume_skb(nskb);
                 return err;
         }
         skb_put(nskb, size);
 
         head_off = skb_headroom(nskb) - skb_headroom(skb);
         skb_headers_offset_update(nskb, head_off);
 
         off = size;
         len = skb->len - off;
         for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) {
                 struct page *page;
                 u32 page_off;
 
                 size = min_t(u32, len, PAGE_SIZE);
                 truesize = size;
 
                 page = page_pool_dev_alloc(pool, &page_off, &truesize);
                 if (!page) {
                         consume_skb(nskb);
                         return -ENOMEM;
                 }
 
                 skb_add_rx_frag(nskb, i, page, page_off, size, truesize);
                 err = skb_copy_bits(skb, off, page_address(page) + page_off,
                                     size);
                 if (err) {
                         consume_skb(nskb);
                         return err;
                 }
 
                 len -= size;
                 off += size;
         }
 
         consume_skb(skb);
         *pskb = nskb;
 
         return 0;
 #else
         return -EOPNOTSUPP;
 #endif
 }
 EXPORT_SYMBOL(skb_pp_cow_data);
 
 int skb_cow_data_for_xdp(struct page_pool *pool, struct sk_buff **pskb,
                          struct bpf_prog *prog)
 {
         if (!prog->aux->xdp_has_frags)
                 return -EINVAL;
 
         return skb_pp_cow_data(pool, pskb, XDP_PACKET_HEADROOM);
 }
 EXPORT_SYMBOL(skb_cow_data_for_xdp);
 
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 bool napi_pp_put_page(netmem_ref netmem)
 {
         struct page *page = netmem_to_page(netmem);
 
         page = compound_head(page);
 
         /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
          * in order to preserve any existing bits, such as bit 0 for the
          * head page of compound page and bit 1 for pfmemalloc page, so
          * mask those bits for freeing side when doing below checking,
          * and page_is_pfmemalloc() is checked in __page_pool_put_page()
          * to avoid recycling the pfmemalloc page.
          */
         if (unlikely(!is_pp_page(page)))
                 return false;
 
         page_pool_put_full_netmem(page->pp, page_to_netmem(page), false);
 
         return true;
 }
 EXPORT_SYMBOL(napi_pp_put_page);
 #endif
 
 static bool skb_pp_recycle(struct sk_buff *skb, void *data)
 {
         if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle)
                 return false;
         return napi_pp_put_page(page_to_netmem(virt_to_page(data)));
 }
 
 /**
  * skb_pp_frag_ref() - Increase fragment references of a page pool aware skb
  * @skb:        page pool aware skb
  *
  * Increase the fragment reference count (pp_ref_count) of a skb. This is
  * intended to gain fragment references only for page pool aware skbs,
  * i.e. when skb->pp_recycle is true, and not for fragments in a
  * non-pp-recycling skb. It has a fallback to increase references on normal
  * pages, as page pool aware skbs may also have normal page fragments.
  */
 static int skb_pp_frag_ref(struct sk_buff *skb)
 {
         struct skb_shared_info *shinfo;
         struct page *head_page;
         int i;
 
         if (!skb->pp_recycle)
                 return -EINVAL;
 
         shinfo = skb_shinfo(skb);
 
         for (i = 0; i < shinfo->nr_frags; i++) {
                 head_page = compound_head(skb_frag_page(&shinfo->frags[i]));
                 if (likely(is_pp_page(head_page)))
                         page_pool_ref_page(head_page);
                 else
                         page_ref_inc(head_page);
         }
         return 0;
 }
 
 static void skb_kfree_head(void *head, unsigned int end_offset)
 {
         if (end_offset == SKB_SMALL_HEAD_HEADROOM)
                 kmem_cache_free(net_hotdata.skb_small_head_cache, head);
         else
                 kfree(head);
 }
 
 static void skb_free_head(struct sk_buff *skb)
 {
         unsigned char *head = skb->head;
 
         if (skb->head_frag) {
                 if (skb_pp_recycle(skb, head))
                         return;
                 skb_free_frag(head);
         } else {
                 skb_kfree_head(head, skb_end_offset(skb));
         }
 }
 
 static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason)
 {
         struct skb_shared_info *shinfo = skb_shinfo(skb);
         int i;
 
         if (!skb_data_unref(skb, shinfo))
                 goto exit;
 
         if (skb_zcopy(skb)) {
                 bool skip_unref = shinfo->flags & SKBFL_MANAGED_FRAG_REFS;
 
                 skb_zcopy_clear(skb, true);
                 if (skip_unref)
                         goto free_head;
         }
 
         for (i = 0; i < shinfo->nr_frags; i++)
                 __skb_frag_unref(&shinfo->frags[i], skb->pp_recycle);
 
 free_head:
         if (shinfo->frag_list)
                 kfree_skb_list_reason(shinfo->frag_list, reason);
 
         skb_free_head(skb);
 exit:
         /* When we clone an SKB we copy the reycling bit. The pp_recycle
          * bit is only set on the head though, so in order to avoid races
          * while trying to recycle fragments on __skb_frag_unref() we need
          * to make one SKB responsible for triggering the recycle path.
          * So disable the recycling bit if an SKB is cloned and we have
          * additional references to the fragmented part of the SKB.
          * Eventually the last SKB will have the recycling bit set and it's
          * dataref set to 0, which will trigger the recycling
          */
         skb->pp_recycle = 0;
 }
 
 /*
  *      Free an skbuff by memory without cleaning the state.
  */
 static void kfree_skbmem(struct sk_buff *skb)
 {
         struct sk_buff_fclones *fclones;
 
         switch (skb->fclone) {
         case SKB_FCLONE_UNAVAILABLE:
                 kmem_cache_free(net_hotdata.skbuff_cache, skb);
                 return;
 
         case SKB_FCLONE_ORIG:
                 fclones = container_of(skb, struct sk_buff_fclones, skb1);
 
                 /* We usually free the clone (TX completion) before original skb
                  * This test would have no chance to be true for the clone,
                  * while here, branch prediction will be good.
                  */
                 if (refcount_read(&fclones->fclone_ref) == 1)
                         goto fastpath;
                 break;
 
         default: /* SKB_FCLONE_CLONE */
                 fclones = container_of(skb, struct sk_buff_fclones, skb2);
                 break;
         }
         if (!refcount_dec_and_test(&fclones->fclone_ref))
                 return;
 fastpath:
         kmem_cache_free(net_hotdata.skbuff_fclone_cache, fclones);
 }
 
 void skb_release_head_state(struct sk_buff *skb)
 {
         skb_dst_drop(skb);
         if (skb->destructor) {
                 DEBUG_NET_WARN_ON_ONCE(in_hardirq());
                 skb->destructor(skb);
         }
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
         nf_conntrack_put(skb_nfct(skb));
 #endif
         skb_ext_put(skb);
 }
 
 /* Free everything but the sk_buff shell. */
 static void skb_release_all(struct sk_buff *skb, enum skb_drop_reason reason)
 {
         skb_release_head_state(skb);
         if (likely(skb->head))
                 skb_release_data(skb, reason);
 }
 
 /**
  *      __kfree_skb - private function
  *      @skb: buffer
  *
  *      Free an sk_buff. Release anything attached to the buffer.
  *      Clean the state. This is an internal helper function. Users should
  *      always call kfree_skb
  */
 
 void __kfree_skb(struct sk_buff *skb)
 {
         skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED);
         kfree_skbmem(skb);
 }
 EXPORT_SYMBOL(__kfree_skb);
 
 static __always_inline
 bool __sk_skb_reason_drop(struct sock *sk, struct sk_buff *skb,
                           enum skb_drop_reason reason)
 {
         if (unlikely(!skb_unref(skb)))
                 return false;
 
         DEBUG_NET_WARN_ON_ONCE(reason == SKB_NOT_DROPPED_YET ||
                                u32_get_bits(reason,
                                             SKB_DROP_REASON_SUBSYS_MASK) >=
                                 SKB_DROP_REASON_SUBSYS_NUM);
 
         if (reason == SKB_CONSUMED)
                 trace_consume_skb(skb, __builtin_return_address(0));
         else
                 trace_kfree_skb(skb, __builtin_return_address(0), reason, sk);
         return true;
 }
 
 /**
  *      sk_skb_reason_drop - free an sk_buff with special reason
  *      @sk: the socket to receive @skb, or NULL if not applicable
  *      @skb: buffer to free
  *      @reason: reason why this skb is dropped
  *
  *      Drop a reference to the buffer and free it if the usage count has hit
  *      zero. Meanwhile, pass the receiving socket and drop reason to
  *      'kfree_skb' tracepoint.
  */
 void __fix_address
 sk_skb_reason_drop(struct sock *sk, struct sk_buff *skb, enum skb_drop_reason reason)
 {
         if (__sk_skb_reason_drop(sk, skb, reason))
                 __kfree_skb(skb);
 }
 EXPORT_SYMBOL(sk_skb_reason_drop);
 
 #define KFREE_SKB_BULK_SIZE     16
 
 struct skb_free_array {
         unsigned int skb_count;
         void *skb_array[KFREE_SKB_BULK_SIZE];
 };
 
 static void kfree_skb_add_bulk(struct sk_buff *skb,
                                struct skb_free_array *sa,
                                enum skb_drop_reason reason)
 {
         /* if SKB is a clone, don't handle this case */
         if (unlikely(skb->fclone != SKB_FCLONE_UNAVAILABLE)) {
                 __kfree_skb(skb);
                 return;
         }
 
         skb_release_all(skb, reason);
         sa->skb_array[sa->skb_count++] = skb;
 
         if (unlikely(sa->skb_count == KFREE_SKB_BULK_SIZE)) {
                 kmem_cache_free_bulk(net_hotdata.skbuff_cache, KFREE_SKB_BULK_SIZE,
                                      sa->skb_array);
                 sa->skb_count = 0;
         }
 }
 
 void __fix_address
 kfree_skb_list_reason(struct sk_buff *segs, enum skb_drop_reason reason)
 {
         struct skb_free_array sa;
 
         sa.skb_count = 0;
 
         while (segs) {
                 struct sk_buff *next = segs->next;
 
                 if (__sk_skb_reason_drop(NULL, segs, reason)) {
                         skb_poison_list(segs);
                         kfree_skb_add_bulk(segs, &sa, reason);
                 }
 
                 segs = next;
         }
 
         if (sa.skb_count)
                 kmem_cache_free_bulk(net_hotdata.skbuff_cache, sa.skb_count, sa.skb_array);
 }
 EXPORT_SYMBOL(kfree_skb_list_reason);
 
 /* Dump skb information and contents.
  *
  * Must only be called from net_ratelimit()-ed paths.
  *
  * Dumps whole packets if full_pkt, only headers otherwise.
  */
 void skb_dump(const char *level, const struct sk_buff *skb, bool full_pkt)
 {
         struct skb_shared_info *sh = skb_shinfo(skb);
         struct net_device *dev = skb->dev;
         struct sock *sk = skb->sk;
         struct sk_buff *list_skb;
         bool has_mac, has_trans;
         int headroom, tailroom;
         int i, len, seg_len;
 
         if (full_pkt)
                 len = skb->len;
         else
                 len = min_t(int, skb->len, MAX_HEADER + 128);
 
         headroom = skb_headroom(skb);
         tailroom = skb_tailroom(skb);
 
         has_mac = skb_mac_header_was_set(skb);
         has_trans = skb_transport_header_was_set(skb);
 
         printk("%sskb len=%u headroom=%u headlen=%u tailroom=%u\n"
                "mac=(%d,%d) mac_len=%u net=(%d,%d) trans=%d\n"
                "shinfo(txflags=%u nr_frags=%u gso(size=%hu type=%u segs=%hu))\n"
                "csum(0x%x start=%u offset=%u ip_summed=%u complete_sw=%u valid=%u level=%u)\n"
                "hash(0x%x sw=%u l4=%u) proto=0x%04x pkttype=%u iif=%d\n"
                "priority=0x%x mark=0x%x alloc_cpu=%u vlan_all=0x%x\n"
                "encapsulation=%d inner(proto=0x%04x, mac=%u, net=%u, trans=%u)\n",
                level, skb->len, headroom, skb_headlen(skb), tailroom,
                has_mac ? skb->mac_header : -1,
                has_mac ? skb_mac_header_len(skb) : -1,
                skb->mac_len,
                skb->network_header,
                has_trans ? skb_network_header_len(skb) : -1,
                has_trans ? skb->transport_header : -1,
                sh->tx_flags, sh->nr_frags,
                sh->gso_size, sh->gso_type, sh->gso_segs,
                skb->csum, skb->csum_start, skb->csum_offset, skb->ip_summed,
                skb->csum_complete_sw, skb->csum_valid, skb->csum_level,
                skb->hash, skb->sw_hash, skb->l4_hash,
                ntohs(skb->protocol), skb->pkt_type, skb->skb_iif,
                skb->priority, skb->mark, skb->alloc_cpu, skb->vlan_all,
                skb->encapsulation, skb->inner_protocol, skb->inner_mac_header,
                skb->inner_network_header, skb->inner_transport_header);
 
         if (dev)
                 printk("%sdev name=%s feat=%pNF\n",
                        level, dev->name, &dev->features);
         if (sk)
                 printk("%ssk family=%hu type=%u proto=%u\n",
                        level, sk->sk_family, sk->sk_type, sk->sk_protocol);
 
         if (full_pkt && headroom)
                 print_hex_dump(level, "skb headroom: ", DUMP_PREFIX_OFFSET,
                                16, 1, skb->head, headroom, false);
 
         seg_len = min_t(int, skb_headlen(skb), len);
         if (seg_len)
                 print_hex_dump(level, "skb linear:   ", DUMP_PREFIX_OFFSET,
                                16, 1, skb->data, seg_len, false);
         len -= seg_len;
 
         if (full_pkt && tailroom)
                 print_hex_dump(level, "skb tailroom: ", DUMP_PREFIX_OFFSET,
                                16, 1, skb_tail_pointer(skb), tailroom, false);
 
         for (i = 0; len && i < skb_shinfo(skb)->nr_frags; i++) {
                 skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
                 u32 p_off, p_len, copied;
                 struct page *p;
                 u8 *vaddr;
 
                 skb_frag_foreach_page(frag, skb_frag_off(frag),
                                       skb_frag_size(frag), p, p_off, p_len,
                                       copied) {
                         seg_len = min_t(int, p_len, len);
                         vaddr = kmap_atomic(p);
                         print_hex_dump(level, "skb frag:     ",
                                        DUMP_PREFIX_OFFSET,
                                        16, 1, vaddr + p_off, seg_len, false);
                         kunmap_atomic(vaddr);
                         len -= seg_len;
                         if (!len)
                                 break;
                 }
         }
 
         if (full_pkt && skb_has_frag_list(skb)) {
                 printk("skb fraglist:\n");
                 skb_walk_frags(skb, list_skb)
                         skb_dump(level, list_skb, true);
         }
 }
 EXPORT_SYMBOL(skb_dump);
 
 /**
  *      skb_tx_error - report an sk_buff xmit error
  *      @skb: buffer that triggered an error
  *
  *      Report xmit error if a device callback is tracking this skb.
  *      skb must be freed afterwards.
  */
 void skb_tx_error(struct sk_buff *skb)
 {
         if (skb) {
                 skb_zcopy_downgrade_managed(skb);
                 skb_zcopy_clear(skb, true);
         }
 }
 EXPORT_SYMBOL(skb_tx_error);
 
 #ifdef CONFIG_TRACEPOINTS
 /**
  *      consume_skb - free an skbuff
  *      @skb: buffer to free
  *
  *      Drop a ref to the buffer and free it if the usage count has hit zero
  *      Functions identically to kfree_skb, but kfree_skb assumes that the frame
  *      is being dropped after a failure and notes that
  */
 void consume_skb(struct sk_buff *skb)
 {
         if (!skb_unref(skb))
                 return;
 
         trace_consume_skb(skb, __builtin_return_address(0));
         __kfree_skb(skb);
 }
 EXPORT_SYMBOL(consume_skb);
 #endif
 
 /**
  *      __consume_stateless_skb - free an skbuff, assuming it is stateless
  *      @skb: buffer to free
  *
  *      Alike consume_skb(), but this variant assumes that this is the last
  *      skb reference and all the head states have been already dropped
  */
 void __consume_stateless_skb(struct sk_buff *skb)
 {
         trace_consume_skb(skb, __builtin_return_address(0));
         skb_release_data(skb, SKB_CONSUMED);
         kfree_skbmem(skb);
 }
 
 static void napi_skb_cache_put(struct sk_buff *skb)
 {
         struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
         u32 i;
 
         if (!kasan_mempool_poison_object(skb))
                 return;
 
         local_lock_nested_bh(&napi_alloc_cache.bh_lock);
         nc->skb_cache[nc->skb_count++] = skb;
 
         if (unlikely(nc->skb_count == NAPI_SKB_CACHE_SIZE)) {
                 for (i = NAPI_SKB_CACHE_HALF; i < NAPI_SKB_CACHE_SIZE; i++)
                         kasan_mempool_unpoison_object(nc->skb_cache[i],
                                                 kmem_cache_size(net_hotdata.skbuff_cache));
 
                 kmem_cache_free_bulk(net_hotdata.skbuff_cache, NAPI_SKB_CACHE_HALF,
                                      nc->skb_cache + NAPI_SKB_CACHE_HALF);
                 nc->skb_count = NAPI_SKB_CACHE_HALF;
         }
         local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
 }
 
 void __napi_kfree_skb(struct sk_buff *skb, enum skb_drop_reason reason)
 {
         skb_release_all(skb, reason);
         napi_skb_cache_put(skb);
 }
 
 void napi_skb_free_stolen_head(struct sk_buff *skb)
 {
         if (unlikely(skb->slow_gro)) {
                 nf_reset_ct(skb);
                 skb_dst_drop(skb);
                 skb_ext_put(skb);
                 skb_orphan(skb);
                 skb->slow_gro = 0;
         }
         napi_skb_cache_put(skb);
 }
 
 void napi_consume_skb(struct sk_buff *skb, int budget)
 {
         /* Zero budget indicate non-NAPI context called us, like netpoll */
         if (unlikely(!budget)) {
                 dev_consume_skb_any(skb);
                 return;
         }
 
         DEBUG_NET_WARN_ON_ONCE(!in_softirq());
 
         if (!skb_unref(skb))
                 return;
 
         /* if reaching here SKB is ready to free */
         trace_consume_skb(skb, __builtin_return_address(0));
 
         /* if SKB is a clone, don't handle this case */
         if (skb->fclone != SKB_FCLONE_UNAVAILABLE) {
                 __kfree_skb(skb);
                 return;
         }
 
         skb_release_all(skb, SKB_CONSUMED);
         napi_skb_cache_put(skb);
 }
 EXPORT_SYMBOL(napi_consume_skb);
 
 /* Make sure a field is contained by headers group */
 #define CHECK_SKB_FIELD(field) \
         BUILD_BUG_ON(offsetof(struct sk_buff, field) !=         \
                      offsetof(struct sk_buff, headers.field));  \
 
 static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 {
         new->tstamp             = old->tstamp;
         /* We do not copy old->sk */
         new->dev                = old->dev;
         memcpy(new->cb, old->cb, sizeof(old->cb));
         skb_dst_copy(new, old);
         __skb_ext_copy(new, old);
         __nf_copy(new, old, false);
 
         /* Note : this field could be in the headers group.
          * It is not yet because we do not want to have a 16 bit hole
          */
         new->queue_mapping = old->queue_mapping;
 
         memcpy(&new->headers, &old->headers, sizeof(new->headers));
         CHECK_SKB_FIELD(protocol);
         CHECK_SKB_FIELD(csum);
         CHECK_SKB_FIELD(hash);
         CHECK_SKB_FIELD(priority);
         CHECK_SKB_FIELD(skb_iif);
         CHECK_SKB_FIELD(vlan_proto);
         CHECK_SKB_FIELD(vlan_tci);
         CHECK_SKB_FIELD(transport_header);
         CHECK_SKB_FIELD(network_header);
         CHECK_SKB_FIELD(mac_header);
         CHECK_SKB_FIELD(inner_protocol);
         CHECK_SKB_FIELD(inner_transport_header);
         CHECK_SKB_FIELD(inner_network_header);
         CHECK_SKB_FIELD(inner_mac_header);
         CHECK_SKB_FIELD(mark);
 #ifdef CONFIG_NETWORK_SECMARK
         CHECK_SKB_FIELD(secmark);
 #endif
 #ifdef CONFIG_NET_RX_BUSY_POLL
         CHECK_SKB_FIELD(napi_id);
 #endif
         CHECK_SKB_FIELD(alloc_cpu);
 #ifdef CONFIG_XPS
         CHECK_SKB_FIELD(sender_cpu);
 #endif
 #ifdef CONFIG_NET_SCHED
         CHECK_SKB_FIELD(tc_index);
 #endif
 
 }
 
 /*
  * You should not add any new code to this function.  Add it to
  * __copy_skb_header above instead.
  */
 static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
 {
 #define C(x) n->x = skb->x
 
         n->next = n->prev = NULL;
         n->sk = NULL;
         __copy_skb_header(n, skb);
 
         C(len);
         C(data_len);
         C(mac_len);
         n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
         n->cloned = 1;
         n->nohdr = 0;
         n->peeked = 0;
         C(pfmemalloc);
         C(pp_recycle);
         n->destructor = NULL;
         C(tail);
         C(end);
         C(head);
         C(head_frag);
         C(data);
         C(truesize);
         refcount_set(&n->users, 1);
 
         atomic_inc(&(skb_shinfo(skb)->dataref));
         skb->cloned = 1;
 
         return n;
 #undef C
 }
 
 /**
  * alloc_skb_for_msg() - allocate sk_buff to wrap frag list forming a msg
  * @first: first sk_buff of the msg
  */
 struct sk_buff *alloc_skb_for_msg(struct sk_buff *first)
 {
         struct sk_buff *n;
 
         n = alloc_skb(0, GFP_ATOMIC);
         if (!n)
                 return NULL;
 
         n->len = first->len;
         n->data_len = first->len;
         n->truesize = first->truesize;
 
         skb_shinfo(n)->frag_list = first;
 
         __copy_skb_header(n, first);
         n->destructor = NULL;
 
         return n;
 }
 EXPORT_SYMBOL_GPL(alloc_skb_for_msg);
 
 /**
  *      skb_morph       -       morph one skb into another
  *      @dst: the skb to receive the contents
  *      @src: the skb to supply the contents
  *
  *      This is identical to skb_clone except that the target skb is
  *      supplied by the user.
  *
  *      The target skb is returned upon exit.
  */
 struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
 {
         skb_release_all(dst, SKB_CONSUMED);
         return __skb_clone(dst, src);
 }
 EXPORT_SYMBOL_GPL(skb_morph);
 
 int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
 {
         unsigned long max_pg, num_pg, new_pg, old_pg, rlim;
         struct user_struct *user;
 
         if (capable(CAP_IPC_LOCK) || !size)
                 return 0;
 
         rlim = rlimit(RLIMIT_MEMLOCK);
         if (rlim == RLIM_INFINITY)
                 return 0;
 
         num_pg = (size >> PAGE_SHIFT) + 2;      /* worst case */
         max_pg = rlim >> PAGE_SHIFT;
         user = mmp->user ? : current_user();
 
         old_pg = atomic_long_read(&user->locked_vm);
         do {
                 new_pg = old_pg + num_pg;
                 if (new_pg > max_pg)
                         return -ENOBUFS;
         } while (!atomic_long_try_cmpxchg(&user->locked_vm, &old_pg, new_pg));
 
         if (!mmp->user) {
                 mmp->user = get_uid(user);
                 mmp->num_pg = num_pg;
         } else {
                 mmp->num_pg += num_pg;
         }
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(mm_account_pinned_pages);
 
 void mm_unaccount_pinned_pages(struct mmpin *mmp)
 {
         if (mmp->user) {
                 atomic_long_sub(mmp->num_pg, &mmp->user->locked_vm);
                 free_uid(mmp->user);
         }
 }
 EXPORT_SYMBOL_GPL(mm_unaccount_pinned_pages);
 
 static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
 {
         struct ubuf_info_msgzc *uarg;
         struct sk_buff *skb;
 
         WARN_ON_ONCE(!in_task());
 
         skb = sock_omalloc(sk, 0, GFP_KERNEL);
         if (!skb)
                 return NULL;
 
         BUILD_BUG_ON(sizeof(*uarg) > sizeof(skb->cb));
         uarg = (void *)skb->cb;
         uarg->mmp.user = NULL;
 
         if (mm_account_pinned_pages(&uarg->mmp, size)) {
                 kfree_skb(skb);
                 return NULL;
         }
 
         uarg->ubuf.ops = &msg_zerocopy_ubuf_ops;
         uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
         uarg->len = 1;
         uarg->bytelen = size;
         uarg->zerocopy = 1;
         uarg->ubuf.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
         refcount_set(&uarg->ubuf.refcnt, 1);
         sock_hold(sk);
 
         return &uarg->ubuf;
 }
 
 static inline struct sk_buff *skb_from_uarg(struct ubuf_info_msgzc *uarg)
 {
         return container_of((void *)uarg, struct sk_buff, cb);
 }
 
 struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
                                        struct ubuf_info *uarg)
 {
         if (uarg) {
                 struct ubuf_info_msgzc *uarg_zc;
                 const u32 byte_limit = 1 << 19;         /* limit to a few TSO */
                 u32 bytelen, next;
 
                 /* there might be non MSG_ZEROCOPY users */
                 if (uarg->ops != &msg_zerocopy_ubuf_ops)
                         return NULL;
 
                 /* realloc only when socket is locked (TCP, UDP cork),
                  * so uarg->len and sk_zckey access is serialized
                  */
                 if (!sock_owned_by_user(sk)) {
                         WARN_ON_ONCE(1);
                         return NULL;
                 }
 
                 uarg_zc = uarg_to_msgzc(uarg);
                 bytelen = uarg_zc->bytelen + size;
                 if (uarg_zc->len == USHRT_MAX - 1 || bytelen > byte_limit) {
                         /* TCP can create new skb to attach new uarg */
                         if (sk->sk_type == SOCK_STREAM)
                                 goto new_alloc;
                         return NULL;
                 }
 
                 next = (u32)atomic_read(&sk->sk_zckey);
                 if ((u32)(uarg_zc->id + uarg_zc->len) == next) {
                         if (mm_account_pinned_pages(&uarg_zc->mmp, size))
                                 return NULL;
                         uarg_zc->len++;
                         uarg_zc->bytelen = bytelen;
                         atomic_set(&sk->sk_zckey, ++next);
 
                         /* no extra ref when appending to datagram (MSG_MORE) */
                         if (sk->sk_type == SOCK_STREAM)
                                 net_zcopy_get(uarg);
 
                         return uarg;
                 }
         }
 
 new_alloc:
         return msg_zerocopy_alloc(sk, size);
 }
 EXPORT_SYMBOL_GPL(msg_zerocopy_realloc);
 
 static bool skb_zerocopy_notify_extend(struct sk_buff *skb, u32 lo, u16 len)
 {
         struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
         u32 old_lo, old_hi;
         u64 sum_len;
 
         old_lo = serr->ee.ee_info;
         old_hi = serr->ee.ee_data;
         sum_len = old_hi - old_lo + 1ULL + len;
 
         if (sum_len >= (1ULL << 32))
                 return false;
 
         if (lo != old_hi + 1)
                 return false;
 
         serr->ee.ee_data += len;
         return true;
 }
 
 static void __msg_zerocopy_callback(struct ubuf_info_msgzc *uarg)
 {
         struct sk_buff *tail, *skb = skb_from_uarg(uarg);
         struct sock_exterr_skb *serr;
         struct sock *sk = skb->sk;
         struct sk_buff_head *q;
         unsigned long flags;
         bool is_zerocopy;
         u32 lo, hi;
         u16 len;
 
         mm_unaccount_pinned_pages(&uarg->mmp);
 
         /* if !len, there was only 1 call, and it was aborted
          * so do not queue a completion notification
          */
         if (!uarg->len || sock_flag(sk, SOCK_DEAD))
                 goto release;
 
         len = uarg->len;
         lo = uarg->id;
         hi = uarg->id + len - 1;
         is_zerocopy = uarg->zerocopy;
 
         serr = SKB_EXT_ERR(skb);
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = 0;
         serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
         serr->ee.ee_data = hi;
         serr->ee.ee_info = lo;
         if (!is_zerocopy)
                 serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED;
 
         q = &sk->sk_error_queue;
         spin_lock_irqsave(&q->lock, flags);
         tail = skb_peek_tail(q);
         if (!tail || SKB_EXT_ERR(tail)->ee.ee_origin != SO_EE_ORIGIN_ZEROCOPY ||
             !skb_zerocopy_notify_extend(tail, lo, len)) {
                 __skb_queue_tail(q, skb);
                 skb = NULL;
         }
         spin_unlock_irqrestore(&q->lock, flags);
 
         sk_error_report(sk);
 
 release:
         consume_skb(skb);
         sock_put(sk);
 }
 
 static void msg_zerocopy_complete(struct sk_buff *skb, struct ubuf_info *uarg,
                                   bool success)
 {
         struct ubuf_info_msgzc *uarg_zc = uarg_to_msgzc(uarg);
 
         uarg_zc->zerocopy = uarg_zc->zerocopy & success;
 
         if (refcount_dec_and_test(&uarg->refcnt))
                 __msg_zerocopy_callback(uarg_zc);
 }
 
 void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 {
         struct sock *sk = skb_from_uarg(uarg_to_msgzc(uarg))->sk;
 
         atomic_dec(&sk->sk_zckey);
         uarg_to_msgzc(uarg)->len--;
 
         if (have_uref)
                 msg_zerocopy_complete(NULL, uarg, true);
 }
 EXPORT_SYMBOL_GPL(msg_zerocopy_put_abort);
 
 const struct ubuf_info_ops msg_zerocopy_ubuf_ops = {
         .complete = msg_zerocopy_complete,
 };
 EXPORT_SYMBOL_GPL(msg_zerocopy_ubuf_ops);
 
 int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
                              struct msghdr *msg, int len,
                              struct ubuf_info *uarg)
 {
         int err, orig_len = skb->len;
 
         if (uarg->ops->link_skb) {
                 err = uarg->ops->link_skb(skb, uarg);
                 if (err)
                         return err;
         } else {
                 struct ubuf_info *orig_uarg = skb_zcopy(skb);
 
                 /* An skb can only point to one uarg. This edge case happens
                  * when TCP appends to an skb, but zerocopy_realloc triggered
                  * a new alloc.
                  */
                 if (orig_uarg && uarg != orig_uarg)
                         return -EEXIST;
         }
 
         err = __zerocopy_sg_from_iter(msg, sk, skb, &msg->msg_iter, len);
         if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
                 struct sock *save_sk = skb->sk;
 
                 /* Streams do not free skb on error. Reset to prev state. */
                 iov_iter_revert(&msg->msg_iter, skb->len - orig_len);
                 skb->sk = sk;
                 ___pskb_trim(skb, orig_len);
                 skb->sk = save_sk;
                 return err;
         }
 
         skb_zcopy_set(skb, uarg, NULL);
         return skb->len - orig_len;
 }
 EXPORT_SYMBOL_GPL(skb_zerocopy_iter_stream);
 
 void __skb_zcopy_downgrade_managed(struct sk_buff *skb)
 {
         int i;
 
         skb_shinfo(skb)->flags &= ~SKBFL_MANAGED_FRAG_REFS;
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                 skb_frag_ref(skb, i);
 }
 EXPORT_SYMBOL_GPL(__skb_zcopy_downgrade_managed);
 
 static int skb_zerocopy_clone(struct sk_buff *nskb, struct sk_buff *orig,
                               gfp_t gfp_mask)
 {
         if (skb_zcopy(orig)) {
                 if (skb_zcopy(nskb)) {
                         /* !gfp_mask callers are verified to !skb_zcopy(nskb) */
                         if (!gfp_mask) {
                                 WARN_ON_ONCE(1);
                                 return -ENOMEM;
                         }
                         if (skb_uarg(nskb) == skb_uarg(orig))
                                 return 0;
                         if (skb_copy_ubufs(nskb, GFP_ATOMIC))
                                 return -EIO;
                 }
                 skb_zcopy_set(nskb, skb_uarg(orig), NULL);
         }
         return 0;
 }
 
 /**
  *      skb_copy_ubufs  -       copy userspace skb frags buffers to kernel
  *      @skb: the skb to modify
  *      @gfp_mask: allocation priority
  *
  *      This must be called on skb with SKBFL_ZEROCOPY_ENABLE.
  *      It will copy all frags into kernel and drop the reference
  *      to userspace pages.
  *
  *      If this function is called from an interrupt gfp_mask() must be
  *      %GFP_ATOMIC.
  *
  *      Returns 0 on success or a negative error code on failure
  *      to allocate kernel memory to copy to.
  */
 int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
 {
         int num_frags = skb_shinfo(skb)->nr_frags;
         struct page *page, *head = NULL;
         int i, order, psize, new_frags;
         u32 d_off;
 
         if (skb_shared(skb) || skb_unclone(skb, gfp_mask))
                 return -EINVAL;
 
         if (!num_frags)
                 goto release;
 
         /* We might have to allocate high order pages, so compute what minimum
          * page order is needed.
          */
         order = 0;
         while ((PAGE_SIZE << order) * MAX_SKB_FRAGS < __skb_pagelen(skb))
                 order++;
         psize = (PAGE_SIZE << order);
 
         new_frags = (__skb_pagelen(skb) + psize - 1) >> (PAGE_SHIFT + order);
         for (i = 0; i < new_frags; i++) {
                 page = alloc_pages(gfp_mask | __GFP_COMP, order);
                 if (!page) {
                         while (head) {
                                 struct page *next = (struct page *)page_private(head);
                                 put_page(head);
                                 head = next;
                         }
                         return -ENOMEM;
                 }
                 set_page_private(page, (unsigned long)head);
                 head = page;
         }
 
         page = head;
         d_off = 0;
         for (i = 0; i < num_frags; i++) {
                 skb_frag_t *f = &skb_shinfo(skb)->frags[i];
                 u32 p_off, p_len, copied;
                 struct page *p;
                 u8 *vaddr;
 
                 skb_frag_foreach_page(f, skb_frag_off(f), skb_frag_size(f),
                                       p, p_off, p_len, copied) {
                         u32 copy, done = 0;
                         vaddr = kmap_atomic(p);
 
                         while (done < p_len) {
                                 if (d_off == psize) {
                                         d_off = 0;
                                         page = (struct page *)page_private(page);
                                 }
                                 copy = min_t(u32, psize - d_off, p_len - done);
                                 memcpy(page_address(page) + d_off,
                                        vaddr + p_off + done, copy);
                                 done += copy;
                                 d_off += copy;
                         }
                         kunmap_atomic(vaddr);
                 }
         }
 
         /* skb frags release userspace buffers */
         for (i = 0; i < num_frags; i++)
                 skb_frag_unref(skb, i);
 
         /* skb frags point to kernel buffers */
         for (i = 0; i < new_frags - 1; i++) {
                 __skb_fill_netmem_desc(skb, i, page_to_netmem(head), 0, psize);
                 head = (struct page *)page_private(head);
         }
         __skb_fill_netmem_desc(skb, new_frags - 1, page_to_netmem(head), 0,
                                d_off);
         skb_shinfo(skb)->nr_frags = new_frags;
 
 release:
         skb_zcopy_clear(skb, false);
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_copy_ubufs);
 
 /**
  *      skb_clone       -       duplicate an sk_buff
  *      @skb: buffer to clone
  *      @gfp_mask: allocation priority
  *
  *      Duplicate an &sk_buff. The new one is not owned by a socket. Both
  *      copies share the same packet data but not structure. The new
  *      buffer has a reference count of 1. If the allocation fails the
  *      function returns %NULL otherwise the new buffer is returned.
  *
  *      If this function is called from an interrupt gfp_mask() must be
  *      %GFP_ATOMIC.
  */
 
 struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 {
         struct sk_buff_fclones *fclones = container_of(skb,
                                                        struct sk_buff_fclones,
                                                        skb1);
         struct sk_buff *n;
 
         if (skb_orphan_frags(skb, gfp_mask))
                 return NULL;
 
         if (skb->fclone == SKB_FCLONE_ORIG &&
             refcount_read(&fclones->fclone_ref) == 1) {
                 n = &fclones->skb2;
                 refcount_set(&fclones->fclone_ref, 2);
                 n->fclone = SKB_FCLONE_CLONE;
         } else {
                 if (skb_pfmemalloc(skb))
                         gfp_mask |= __GFP_MEMALLOC;
 
                 n = kmem_cache_alloc(net_hotdata.skbuff_cache, gfp_mask);
                 if (!n)
                         return NULL;
 
                 n->fclone = SKB_FCLONE_UNAVAILABLE;
         }
 
         return __skb_clone(n, skb);
 }
 EXPORT_SYMBOL(skb_clone);
 
 void skb_headers_offset_update(struct sk_buff *skb, int off)
 {
         /* Only adjust this if it actually is csum_start rather than csum */
         if (skb->ip_summed == CHECKSUM_PARTIAL)
                 skb->csum_start += off;
         /* {transport,network,mac}_header and tail are relative to skb->head */
         skb->transport_header += off;
         skb->network_header   += off;
         if (skb_mac_header_was_set(skb))
                 skb->mac_header += off;
         skb->inner_transport_header += off;
         skb->inner_network_header += off;
         skb->inner_mac_header += off;
 }
 EXPORT_SYMBOL(skb_headers_offset_update);
 
 void skb_copy_header(struct sk_buff *new, const struct sk_buff *old)
 {
         __copy_skb_header(new, old);
 
         skb_shinfo(new)->gso_size = skb_shinfo(old)->gso_size;
         skb_shinfo(new)->gso_segs = skb_shinfo(old)->gso_segs;
         skb_shinfo(new)->gso_type = skb_shinfo(old)->gso_type;
 }
 EXPORT_SYMBOL(skb_copy_header);
 
 static inline int skb_alloc_rx_flag(const struct sk_buff *skb)
 {
         if (skb_pfmemalloc(skb))
                 return SKB_ALLOC_RX;
         return 0;
 }
 
 /**
  *      skb_copy        -       create private copy of an sk_buff
  *      @skb: buffer to copy
  *      @gfp_mask: allocation priority
  *
  *      Make a copy of both an &sk_buff and its data. This is used when the
  *      caller wishes to modify the data and needs a private copy of the
  *      data to alter. Returns %NULL on failure or the pointer to the buffer
  *      on success. The returned buffer has a reference count of 1.
  *
  *      As by-product this function converts non-linear &sk_buff to linear
  *      one, so that &sk_buff becomes completely private and caller is allowed
  *      to modify all the data of returned buffer. This means that this
  *      function is not recommended for use in circumstances when only
  *      header is going to be modified. Use pskb_copy() instead.
  */
 
 struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t gfp_mask)
 {
         struct sk_buff *n;
         unsigned int size;
         int headerlen;
 
         if (WARN_ON_ONCE(skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST))
                 return NULL;
 
         headerlen = skb_headroom(skb);
         size = skb_end_offset(skb) + skb->data_len;
         n = __alloc_skb(size, gfp_mask,
                         skb_alloc_rx_flag(skb), NUMA_NO_NODE);
         if (!n)
                 return NULL;
 
         /* Set the data pointer */
         skb_reserve(n, headerlen);
         /* Set the tail pointer and length */
         skb_put(n, skb->len);
 
         BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len));
 
         skb_copy_header(n, skb);
         return n;
 }
 EXPORT_SYMBOL(skb_copy);
 
 /**
  *      __pskb_copy_fclone      -  create copy of an sk_buff with private head.
  *      @skb: buffer to copy
  *      @headroom: headroom of new skb
  *      @gfp_mask: allocation priority
  *      @fclone: if true allocate the copy of the skb from the fclone
  *      cache instead of the head cache; it is recommended to set this
  *      to true for the cases where the copy will likely be cloned
  *
  *      Make a copy of both an &sk_buff and part of its data, located
  *      in header. Fragmented data remain shared. This is used when
  *      the caller wishes to modify only header of &sk_buff and needs
  *      private copy of the header to alter. Returns %NULL on failure
  *      or the pointer to the buffer on success.
  *      The returned buffer has a reference count of 1.
  */
 
 struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
                                    gfp_t gfp_mask, bool fclone)
 {
         unsigned int size = skb_headlen(skb) + headroom;
         int flags = skb_alloc_rx_flag(skb) | (fclone ? SKB_ALLOC_FCLONE : 0);
         struct sk_buff *n = __alloc_skb(size, gfp_mask, flags, NUMA_NO_NODE);
 
         if (!n)
                 goto out;
 
         /* Set the data pointer */
         skb_reserve(n, headroom);
         /* Set the tail pointer and length */
         skb_put(n, skb_headlen(skb));
         /* Copy the bytes */
         skb_copy_from_linear_data(skb, n->data, n->len);
 
         n->truesize += skb->data_len;
         n->data_len  = skb->data_len;
         n->len       = skb->len;
 
         if (skb_shinfo(skb)->nr_frags) {
                 int i;
 
                 if (skb_orphan_frags(skb, gfp_mask) ||
                     skb_zerocopy_clone(n, skb, gfp_mask)) {
                         kfree_skb(n);
                         n = NULL;
                         goto out;
                 }
                 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                         skb_shinfo(n)->frags[i] = skb_shinfo(skb)->frags[i];
                         skb_frag_ref(skb, i);
                 }
                 skb_shinfo(n)->nr_frags = i;
         }
 
         if (skb_has_frag_list(skb)) {
                 skb_shinfo(n)->frag_list = skb_shinfo(skb)->frag_list;
                 skb_clone_fraglist(n);
         }
 
         skb_copy_header(n, skb);
 out:
         return n;
 }
 EXPORT_SYMBOL(__pskb_copy_fclone);
 
 /**
  *      pskb_expand_head - reallocate header of &sk_buff
  *      @skb: buffer to reallocate
  *      @nhead: room to add at head
  *      @ntail: room to add at tail
  *      @gfp_mask: allocation priority
  *
  *      Expands (or creates identical copy, if @nhead and @ntail are zero)
  *      header of @skb. &sk_buff itself is not changed. &sk_buff MUST have
  *      reference count of 1. Returns zero in the case of success or error,
  *      if expansion failed. In the last case, &sk_buff is not changed.
  *
  *      All the pointers pointing into skb header may change and must be
  *      reloaded after call to this function.
  */
 
 int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
                      gfp_t gfp_mask)
 {
         unsigned int osize = skb_end_offset(skb);
         unsigned int size = osize + nhead + ntail;
         long off;
         u8 *data;
         int i;
 
         BUG_ON(nhead < 0);
 
         BUG_ON(skb_shared(skb));
 
         skb_zcopy_downgrade_managed(skb);
 
         if (skb_pfmemalloc(skb))
                 gfp_mask |= __GFP_MEMALLOC;
 
         data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
         if (!data)
                 goto nodata;
         size = SKB_WITH_OVERHEAD(size);
 
         /* Copy only real data... and, alas, header. This should be
          * optimized for the cases when header is void.
          */
         memcpy(data + nhead, skb->head, skb_tail_pointer(skb) - skb->head);
 
         memcpy((struct skb_shared_info *)(data + size),
                skb_shinfo(skb),
                offsetof(struct skb_shared_info, frags[skb_shinfo(skb)->nr_frags]));
 
         /*
          * if shinfo is shared we must drop the old head gracefully, but if it
          * is not we can just drop the old head and let the existing refcount
          * be since all we did is relocate the values
          */
         if (skb_cloned(skb)) {
                 if (skb_orphan_frags(skb, gfp_mask))
                         goto nofrags;
                 if (skb_zcopy(skb))
                         refcount_inc(&skb_uarg(skb)->refcnt);
                 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                         skb_frag_ref(skb, i);
 
                 if (skb_has_frag_list(skb))
                         skb_clone_fraglist(skb);
 
                 skb_release_data(skb, SKB_CONSUMED);
         } else {
                 skb_free_head(skb);
         }
         off = (data + nhead) - skb->head;
 
         skb->head     = data;
         skb->head_frag = 0;
         skb->data    += off;
 
         skb_set_end_offset(skb, size);
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
         off           = nhead;
 #endif
         skb->tail             += off;
         skb_headers_offset_update(skb, nhead);
         skb->cloned   = 0;
         skb->hdr_len  = 0;
         skb->nohdr    = 0;
         atomic_set(&skb_shinfo(skb)->dataref, 1);
 
         skb_metadata_clear(skb);
 
         /* It is not generally safe to change skb->truesize.
          * For the moment, we really care of rx path, or
          * when skb is orphaned (not attached to a socket).
          */
         if (!skb->sk || skb->destructor == sock_edemux)
                 skb->truesize += size - osize;
 
         return 0;
 
 nofrags:
         skb_kfree_head(data, size);
 nodata:
         return -ENOMEM;
 }
 EXPORT_SYMBOL(pskb_expand_head);
 
 /* Make private copy of skb with writable head and some headroom */
 
 struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)
 {
         struct sk_buff *skb2;
         int delta = headroom - skb_headroom(skb);
 
         if (delta <= 0)
                 skb2 = pskb_copy(skb, GFP_ATOMIC);
         else {
                 skb2 = skb_clone(skb, GFP_ATOMIC);
                 if (skb2 && pskb_expand_head(skb2, SKB_DATA_ALIGN(delta), 0,
                                              GFP_ATOMIC)) {
                         kfree_skb(skb2);
                         skb2 = NULL;
                 }
         }
         return skb2;
 }
 EXPORT_SYMBOL(skb_realloc_headroom);
 
 /* Note: We plan to rework this in linux-6.4 */
 int __skb_unclone_keeptruesize(struct sk_buff *skb, gfp_t pri)
 {
         unsigned int saved_end_offset, saved_truesize;
         struct skb_shared_info *shinfo;
         int res;
 
         saved_end_offset = skb_end_offset(skb);
         saved_truesize = skb->truesize;
 
         res = pskb_expand_head(skb, 0, 0, pri);
         if (res)
                 return res;
 
         skb->truesize = saved_truesize;
 
         if (likely(skb_end_offset(skb) == saved_end_offset))
                 return 0;
 
         /* We can not change skb->end if the original or new value
          * is SKB_SMALL_HEAD_HEADROOM, as it might break skb_kfree_head().
          */
         if (saved_end_offset == SKB_SMALL_HEAD_HEADROOM ||
             skb_end_offset(skb) == SKB_SMALL_HEAD_HEADROOM) {
                 /* We think this path should not be taken.
                  * Add a temporary trace to warn us just in case.
                  */
                 pr_err_once("__skb_unclone_keeptruesize() skb_end_offset() %u -> %u\n",
                             saved_end_offset, skb_end_offset(skb));
                 WARN_ON_ONCE(1);
                 return 0;
         }
 
         shinfo = skb_shinfo(skb);
 
         /* We are about to change back skb->end,
          * we need to move skb_shinfo() to its new location.
          */
         memmove(skb->head + saved_end_offset,
                 shinfo,
                 offsetof(struct skb_shared_info, frags[shinfo->nr_frags]));
 
         skb_set_end_offset(skb, saved_end_offset);
 
         return 0;
 }
 
 /**
  *      skb_expand_head - reallocate header of &sk_buff
  *      @skb: buffer to reallocate
  *      @headroom: needed headroom
  *
  *      Unlike skb_realloc_headroom, this one does not allocate a new skb
  *      if possible; copies skb->sk to new skb as needed
  *      and frees original skb in case of failures.
  *
  *      It expect increased headroom and generates warning otherwise.
  */
 
 struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
 {
         int delta = headroom - skb_headroom(skb);
         int osize = skb_end_offset(skb);
         struct sock *sk = skb->sk;
 
         if (WARN_ONCE(delta <= 0,
                       "%s is expecting an increase in the headroom", __func__))
                 return skb;
 
         delta = SKB_DATA_ALIGN(delta);
         /* pskb_expand_head() might crash, if skb is shared. */
         if (skb_shared(skb) || !is_skb_wmem(skb)) {
                 struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
 
                 if (unlikely(!nskb))
                         goto fail;
 
                 if (sk)
                         skb_set_owner_w(nskb, sk);
                 consume_skb(skb);
                 skb = nskb;
         }
         if (pskb_expand_head(skb, delta, 0, GFP_ATOMIC))
                 goto fail;
 
         if (sk && is_skb_wmem(skb)) {
                 delta = skb_end_offset(skb) - osize;
                 refcount_add(delta, &sk->sk_wmem_alloc);
                 skb->truesize += delta;
         }
         return skb;
 
 fail:
         kfree_skb(skb);
         return NULL;
 }
 EXPORT_SYMBOL(skb_expand_head);
 
 /**
  *      skb_copy_expand -       copy and expand sk_buff
  *      @skb: buffer to copy
  *      @newheadroom: new free bytes at head
  *      @newtailroom: new free bytes at tail
  *      @gfp_mask: allocation priority
  *
  *      Make a copy of both an &sk_buff and its data and while doing so
  *      allocate additional space.
  *
  *      This is used when the caller wishes to modify the data and needs a
  *      private copy of the data to alter as well as more space for new fields.
  *      Returns %NULL on failure or the pointer to the buffer
  *      on success. The returned buffer has a reference count of 1.
  *
  *      You must pass %GFP_ATOMIC as the allocation priority if this function
  *      is called from an interrupt.
  */
 struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
                                 int newheadroom, int newtailroom,
                                 gfp_t gfp_mask)
 {
         /*
          *      Allocate the copy buffer
          */
         int head_copy_len, head_copy_off;
         struct sk_buff *n;
         int oldheadroom;
 
         if (WARN_ON_ONCE(skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST))
                 return NULL;
 
         oldheadroom = skb_headroom(skb);
         n = __alloc_skb(newheadroom + skb->len + newtailroom,
                         gfp_mask, skb_alloc_rx_flag(skb),
                         NUMA_NO_NODE);
         if (!n)
                 return NULL;
 
         skb_reserve(n, newheadroom);
 
         /* Set the tail pointer and length */
         skb_put(n, skb->len);
 
         head_copy_len = oldheadroom;
         head_copy_off = 0;
         if (newheadroom <= head_copy_len)
                 head_copy_len = newheadroom;
         else
                 head_copy_off = newheadroom - head_copy_len;
 
         /* Copy the linear header and data. */
         BUG_ON(skb_copy_bits(skb, -head_copy_len, n->head + head_copy_off,
                              skb->len + head_copy_len));
 
         skb_copy_header(n, skb);
 
         skb_headers_offset_update(n, newheadroom - oldheadroom);
 
         return n;
 }
 EXPORT_SYMBOL(skb_copy_expand);
 
 /**
  *      __skb_pad               -       zero pad the tail of an skb
  *      @skb: buffer to pad
  *      @pad: space to pad
  *      @free_on_error: free buffer on error
  *
  *      Ensure that a buffer is followed by a padding area that is zero
  *      filled. Used by network drivers which may DMA or transfer data
  *      beyond the buffer end onto the wire.
  *
  *      May return error in out of memory cases. The skb is freed on error
  *      if @free_on_error is true.
  */
 
 int __skb_pad(struct sk_buff *skb, int pad, bool free_on_error)
 {
         int err;
         int ntail;
 
         /* If the skbuff is non linear tailroom is always zero.. */
         if (!skb_cloned(skb) && skb_tailroom(skb) >= pad) {
                 memset(skb->data+skb->len, 0, pad);
                 return 0;
         }
 
         ntail = skb->data_len + pad - (skb->end - skb->tail);
         if (likely(skb_cloned(skb) || ntail > 0)) {
                 err = pskb_expand_head(skb, 0, ntail, GFP_ATOMIC);
                 if (unlikely(err))
                         goto free_skb;
         }
 
         /* FIXME: The use of this function with non-linear skb's really needs
          * to be audited.
          */
         err = skb_linearize(skb);
         if (unlikely(err))
                 goto free_skb;
 
         memset(skb->data + skb->len, 0, pad);
         return 0;
 
 free_skb:
         if (free_on_error)
                 kfree_skb(skb);
         return err;
 }
 EXPORT_SYMBOL(__skb_pad);
 
 /**
  *      pskb_put - add data to the tail of a potentially fragmented buffer
  *      @skb: start of the buffer to use
  *      @tail: tail fragment of the buffer to use
  *      @len: amount of data to add
  *
  *      This function extends the used data area of the potentially
  *      fragmented buffer. @tail must be the last fragment of @skb -- or
  *      @skb itself. If this would exceed the total buffer size the kernel
  *      will panic. A pointer to the first byte of the extra data is
  *      returned.
  */
 
 void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len)
 {
         if (tail != skb) {
                 skb->data_len += len;
                 skb->len += len;
         }
         return skb_put(tail, len);
 }
 EXPORT_SYMBOL_GPL(pskb_put);
 
 /**
  *      skb_put - add data to a buffer
  *      @skb: buffer to use
  *      @len: amount of data to add
  *
  *      This function extends the used data area of the buffer. If this would
  *      exceed the total buffer size the kernel will panic. A pointer to the
  *      first byte of the extra data is returned.
  */
 void *skb_put(struct sk_buff *skb, unsigned int len)
 {
         void *tmp = skb_tail_pointer(skb);
         SKB_LINEAR_ASSERT(skb);
         skb->tail += len;
         skb->len  += len;
         if (unlikely(skb->tail > skb->end))
                 skb_over_panic(skb, len, __builtin_return_address(0));
         return tmp;
 }
 EXPORT_SYMBOL(skb_put);
 
 /**
  *      skb_push - add data to the start of a buffer
  *      @skb: buffer to use
  *      @len: amount of data to add
  *
  *      This function extends the used data area of the buffer at the buffer
  *      start. If this would exceed the total buffer headroom the kernel will
  *      panic. A pointer to the first byte of the extra data is returned.
  */
 void *skb_push(struct sk_buff *skb, unsigned int len)
 {
         skb->data -= len;
         skb->len  += len;
         if (unlikely(skb->data < skb->head))
                 skb_under_panic(skb, len, __builtin_return_address(0));
         return skb->data;
 }
 EXPORT_SYMBOL(skb_push);
 
 /**
  *      skb_pull - remove data from the start of a buffer
  *      @skb: buffer to use
  *      @len: amount of data to remove
  *
  *      This function removes data from the start of a buffer, returning
  *      the memory to the headroom. A pointer to the next data in the buffer
  *      is returned. Once the data has been pulled future pushes will overwrite
  *      the old data.
  */
 void *skb_pull(struct sk_buff *skb, unsigned int len)
 {
         return skb_pull_inline(skb, len);
 }
 EXPORT_SYMBOL(skb_pull);
 
 /**
  *      skb_pull_data - remove data from the start of a buffer returning its
  *      original position.
  *      @skb: buffer to use
  *      @len: amount of data to remove
  *
  *      This function removes data from the start of a buffer, returning
  *      the memory to the headroom. A pointer to the original data in the buffer
  *      is returned after checking if there is enough data to pull. Once the
  *      data has been pulled future pushes will overwrite the old data.
  */
 void *skb_pull_data(struct sk_buff *skb, size_t len)
 {
         void *data = skb->data;
 
         if (skb->len < len)
                 return NULL;
 
         skb_pull(skb, len);
 
         return data;
 }
 EXPORT_SYMBOL(skb_pull_data);
 
 /**
  *      skb_trim - remove end from a buffer
  *      @skb: buffer to alter
  *      @len: new length
  *
  *      Cut the length of a buffer down by removing data from the tail. If
  *      the buffer is already under the length specified it is not modified.
  *      The skb must be linear.
  */
 void skb_trim(struct sk_buff *skb, unsigned int len)
 {
         if (skb->len > len)
                 __skb_trim(skb, len);
 }
 EXPORT_SYMBOL(skb_trim);
 
 /* Trims skb to length len. It can change skb pointers.
  */
 
 int ___pskb_trim(struct sk_buff *skb, unsigned int len)
 {
         struct sk_buff **fragp;
         struct sk_buff *frag;
         int offset = skb_headlen(skb);
         int nfrags = skb_shinfo(skb)->nr_frags;
         int i;
         int err;
 
         if (skb_cloned(skb) &&
             unlikely((err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC))))
                 return err;
 
         i = 0;
         if (offset >= len)
                 goto drop_pages;
 
         for (; i < nfrags; i++) {
                 int end = offset + skb_frag_size(&skb_shinfo(skb)->frags[i]);
 
                 if (end < len) {
                         offset = end;
                         continue;
                 }
 
                 skb_frag_size_set(&skb_shinfo(skb)->frags[i++], len - offset);
 
 drop_pages:
                 skb_shinfo(skb)->nr_frags = i;
 
                 for (; i < nfrags; i++)
                         skb_frag_unref(skb, i);
 
                 if (skb_has_frag_list(skb))
                         skb_drop_fraglist(skb);
                 goto done;
         }
 
         for (fragp = &skb_shinfo(skb)->frag_list; (frag = *fragp);
              fragp = &frag->next) {
                 int end = offset + frag->len;
 
                 if (skb_shared(frag)) {
                         struct sk_buff *nfrag;
 
                         nfrag = skb_clone(frag, GFP_ATOMIC);
                         if (unlikely(!nfrag))
                                 return -ENOMEM;
 
                         nfrag->next = frag->next;
                         consume_skb(frag);
                         frag = nfrag;
                         *fragp = frag;
                 }
 
                 if (end < len) {
                         offset = end;
                         continue;
                 }
 
                 if (end > len &&
                     unlikely((err = pskb_trim(frag, len - offset))))
                         return err;
 
                 if (frag->next)
                         skb_drop_list(&frag->next);
                 break;
         }
 
 done:
         if (len > skb_headlen(skb)) {
                 skb->data_len -= skb->len - len;
                 skb->len       = len;
         } else {
                 skb->len       = len;
                 skb->data_len  = 0;
                 skb_set_tail_pointer(skb, len);
         }
 
         if (!skb->sk || skb->destructor == sock_edemux)
                 skb_condense(skb);
         return 0;
 }
 EXPORT_SYMBOL(___pskb_trim);
 
 /* Note : use pskb_trim_rcsum() instead of calling this directly
  */
 int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
 {
         if (skb->ip_summed == CHECKSUM_COMPLETE) {
                 int delta = skb->len - len;
 
                 skb->csum = csum_block_sub(skb->csum,
                                            skb_checksum(skb, len, delta, 0),
                                            len);
         } else if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 int hdlen = (len > skb_headlen(skb)) ? skb_headlen(skb) : len;
                 int offset = skb_checksum_start_offset(skb) + skb->csum_offset;
 
                 if (offset + sizeof(__sum16) > hdlen)
                         return -EINVAL;
         }
         return __pskb_trim(skb, len);
 }
 EXPORT_SYMBOL(pskb_trim_rcsum_slow);
 
 /**
  *      __pskb_pull_tail - advance tail of skb header
  *      @skb: buffer to reallocate
  *      @delta: number of bytes to advance tail
  *
  *      The function makes a sense only on a fragmented &sk_buff,
  *      it expands header moving its tail forward and copying necessary
  *      data from fragmented part.
  *
  *      &sk_buff MUST have reference count of 1.
  *
  *      Returns %NULL (and &sk_buff does not change) if pull failed
  *      or value of new tail of skb in the case of success.
  *
  *      All the pointers pointing into skb header may change and must be
  *      reloaded after call to this function.
  */
 
 /* Moves tail of skb head forward, copying data from fragmented part,
  * when it is necessary.
  * 1. It may fail due to malloc failure.
  * 2. It may change skb pointers.
  *
  * It is pretty complicated. Luckily, it is called only in exceptional cases.
  */
 void *__pskb_pull_tail(struct sk_buff *skb, int delta)
 {
         /* If skb has not enough free space at tail, get new one
          * plus 128 bytes for future expansions. If we have enough
          * room at tail, reallocate without expansion only if skb is cloned.
          */
         int i, k, eat = (skb->tail + delta) - skb->end;
 
         if (eat > 0 || skb_cloned(skb)) {
                 if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
                                      GFP_ATOMIC))
                         return NULL;
         }
 
         BUG_ON(skb_copy_bits(skb, skb_headlen(skb),
                              skb_tail_pointer(skb), delta));
 
         /* Optimization: no fragments, no reasons to preestimate
          * size of pulled pages. Superb.
          */
         if (!skb_has_frag_list(skb))
                 goto pull_pages;
 
         /* Estimate size of pulled pages. */
         eat = delta;
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
 
                 if (size >= eat)
                         goto pull_pages;
                 eat -= size;
         }
 
         /* If we need update frag list, we are in troubles.
          * Certainly, it is possible to add an offset to skb data,
          * but taking into account that pulling is expected to
          * be very rare operation, it is worth to fight against
          * further bloating skb head and crucify ourselves here instead.
          * Pure masohism, indeed. 8)8)
          */
         if (eat) {
                 struct sk_buff *list = skb_shinfo(skb)->frag_list;
                 struct sk_buff *clone = NULL;
                 struct sk_buff *insp = NULL;
 
                 do {
                         if (list->len <= eat) {
                                 /* Eaten as whole. */
                                 eat -= list->len;
                                 list = list->next;
                                 insp = list;
                         } else {
                                 /* Eaten partially. */
                                 if (skb_is_gso(skb) && !list->head_frag &&
                                     skb_headlen(list))
                                         skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
 
                                 if (skb_shared(list)) {
                                         /* Sucks! We need to fork list. :-( */
                                         clone = skb_clone(list, GFP_ATOMIC);
                                         if (!clone)
                                                 return NULL;
                                         insp = list->next;
                                         list = clone;
                                 } else {
                                         /* This may be pulled without
                                          * problems. */
                                         insp = list;
                                 }
                                 if (!pskb_pull(list, eat)) {
                                         kfree_skb(clone);
                                         return NULL;
                                 }
                                 break;
                         }
                 } while (eat);
 
                 /* Free pulled out fragments. */
                 while ((list = skb_shinfo(skb)->frag_list) != insp) {
                         skb_shinfo(skb)->frag_list = list->next;
                         consume_skb(list);
                 }
                 /* And insert new clone at head. */
                 if (clone) {
                         clone->next = list;
                         skb_shinfo(skb)->frag_list = clone;
                 }
         }
         /* Success! Now we may commit changes to skb data. */
 
 pull_pages:
         eat = delta;
         k = 0;
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
 
                 if (size <= eat) {
                         skb_frag_unref(skb, i);
                         eat -= size;
                 } else {
                         skb_frag_t *frag = &skb_shinfo(skb)->frags[k];
 
                         *frag = skb_shinfo(skb)->frags[i];
                         if (eat) {
                                 skb_frag_off_add(frag, eat);
                                 skb_frag_size_sub(frag, eat);
                                 if (!i)
                                         goto end;
                                 eat = 0;
                         }
                         k++;
                 }
         }
         skb_shinfo(skb)->nr_frags = k;
 
 end:
         skb->tail     += delta;
         skb->data_len -= delta;
 
         if (!skb->data_len)
                 skb_zcopy_clear(skb, false);
 
         return skb_tail_pointer(skb);
 }
 EXPORT_SYMBOL(__pskb_pull_tail);
 
 /**
  *      skb_copy_bits - copy bits from skb to kernel buffer
  *      @skb: source skb
  *      @offset: offset in source
  *      @to: destination buffer
  *      @len: number of bytes to copy
  *
  *      Copy the specified number of bytes from the source skb to the
  *      destination buffer.
  *
  *      CAUTION ! :
  *              If its prototype is ever changed,
  *              check arch/{*}/net/{*}.S files,
  *              since it is called from BPF assembly code.
  */
 int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
 {
         int start = skb_headlen(skb);
         struct sk_buff *frag_iter;
         int i, copy;
 
         if (offset > (int)skb->len - len)
                 goto fault;
 
         /* Copy header. */
         if ((copy = start - offset) > 0) {
                 if (copy > len)
                         copy = len;
                 skb_copy_from_linear_data_offset(skb, offset, to, copy);
                 if ((len -= copy) == 0)
                         return 0;
                 offset += copy;
                 to     += copy;
         }
 
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int end;
                 skb_frag_t *f = &skb_shinfo(skb)->frags[i];
 
                 WARN_ON(start > offset + len);
 
                 end = start + skb_frag_size(f);
                 if ((copy = end - offset) > 0) {
                         u32 p_off, p_len, copied;
                         struct page *p;
                         u8 *vaddr;
 
                         if (copy > len)
                                 copy = len;
 
                         skb_frag_foreach_page(f,
                                               skb_frag_off(f) + offset - start,
                                               copy, p, p_off, p_len, copied) {
                                 vaddr = kmap_atomic(p);
                                 memcpy(to + copied, vaddr + p_off, p_len);
                                 kunmap_atomic(vaddr);
                         }
 
                         if ((len -= copy) == 0)
                                 return 0;
                         offset += copy;
                         to     += copy;
                 }
                 start = end;
         }
 
         skb_walk_frags(skb, frag_iter) {
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + frag_iter->len;
                 if ((copy = end - offset) > 0) {
                         if (copy > len)
                                 copy = len;
                         if (skb_copy_bits(frag_iter, offset - start, to, copy))
                                 goto fault;
                         if ((len -= copy) == 0)
                                 return 0;
                         offset += copy;
                         to     += copy;
                 }
                 start = end;
         }
 
         if (!len)
                 return 0;
 
 fault:
         return -EFAULT;
 }
 EXPORT_SYMBOL(skb_copy_bits);
 
 /*
  * Callback from splice_to_pipe(), if we need to release some pages
  * at the end of the spd in case we error'ed out in filling the pipe.
  */
 static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
 {
         put_page(spd->pages[i]);
 }
 
 static struct page *linear_to_page(struct page *page, unsigned int *len,
                                    unsigned int *offset,
                                    struct sock *sk)
 {
         struct page_frag *pfrag = sk_page_frag(sk);
 
         if (!sk_page_frag_refill(sk, pfrag))
                 return NULL;
 
         *len = min_t(unsigned int, *len, pfrag->size - pfrag->offset);
 
         memcpy(page_address(pfrag->page) + pfrag->offset,
                page_address(page) + *offset, *len);
         *offset = pfrag->offset;
         pfrag->offset += *len;
 
         return pfrag->page;
 }
 
 static bool spd_can_coalesce(const struct splice_pipe_desc *spd,
                              struct page *page,
                              unsigned int offset)
 {
         return  spd->nr_pages &&
                 spd->pages[spd->nr_pages - 1] == page &&
                 (spd->partial[spd->nr_pages - 1].offset +
                  spd->partial[spd->nr_pages - 1].len == offset);
 }
 
 /*
  * Fill page/offset/length into spd, if it can hold more pages.
  */
 static bool spd_fill_page(struct splice_pipe_desc *spd,
                           struct pipe_inode_info *pipe, struct page *page,
                           unsigned int *len, unsigned int offset,
                           bool linear,
                           struct sock *sk)
 {
         if (unlikely(spd->nr_pages == MAX_SKB_FRAGS))
                 return true;
 
         if (linear) {
                 page = linear_to_page(page, len, &offset, sk);
                 if (!page)
                         return true;
         }
         if (spd_can_coalesce(spd, page, offset)) {
                 spd->partial[spd->nr_pages - 1].len += *len;
                 return false;
         }
         get_page(page);
         spd->pages[spd->nr_pages] = page;
         spd->partial[spd->nr_pages].len = *len;
         spd->partial[spd->nr_pages].offset = offset;
         spd->nr_pages++;
 
         return false;
 }
 
 static bool __splice_segment(struct page *page, unsigned int poff,
                              unsigned int plen, unsigned int *off,
                              unsigned int *len,
                              struct splice_pipe_desc *spd, bool linear,
                              struct sock *sk,
                              struct pipe_inode_info *pipe)
 {
         if (!*len)
                 return true;
 
         /* skip this segment if already processed */
         if (*off >= plen) {
                 *off -= plen;
                 return false;
         }
 
         /* ignore any bits we already processed */
         poff += *off;
         plen -= *off;
         *off = 0;
 
         do {
                 unsigned int flen = min(*len, plen);
 
                 if (spd_fill_page(spd, pipe, page, &flen, poff,
                                   linear, sk))
                         return true;
                 poff += flen;
                 plen -= flen;
                 *len -= flen;
         } while (*len && plen);
 
         return false;
 }
 
 /*
  * Map linear and fragment data from the skb to spd. It reports true if the
  * pipe is full or if we already spliced the requested length.
  */
 static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
                               unsigned int *offset, unsigned int *len,
                               struct splice_pipe_desc *spd, struct sock *sk)
 {
         int seg;
         struct sk_buff *iter;
 
         /* map the linear part :
          * If skb->head_frag is set, this 'linear' part is backed by a
          * fragment, and if the head is not shared with any clones then
          * we can avoid a copy since we own the head portion of this page.
          */
         if (__splice_segment(virt_to_page(skb->data),
                              (unsigned long) skb->data & (PAGE_SIZE - 1),
                              skb_headlen(skb),
                              offset, len, spd,
                              skb_head_is_locked(skb),
                              sk, pipe))
                 return true;
 
         /*
          * then map the fragments
          */
         for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
                 const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
 
                 if (__splice_segment(skb_frag_page(f),
                                      skb_frag_off(f), skb_frag_size(f),
                                      offset, len, spd, false, sk, pipe))
                         return true;
         }
 
         skb_walk_frags(skb, iter) {
                 if (*offset >= iter->len) {
                         *offset -= iter->len;
                         continue;
                 }
                 /* __skb_splice_bits() only fails if the output has no room
                  * left, so no point in going over the frag_list for the error
                  * case.
                  */
                 if (__skb_splice_bits(iter, pipe, offset, len, spd, sk))
                         return true;
         }
 
         return false;
 }
 
 /*
  * Map data from the skb to a pipe. Should handle both the linear part,
  * the fragments, and the frag list.
  */
 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
                     struct pipe_inode_info *pipe, unsigned int tlen,
                     unsigned int flags)
 {
         struct partial_page partial[MAX_SKB_FRAGS];
         struct page *pages[MAX_SKB_FRAGS];
         struct splice_pipe_desc spd = {
                 .pages = pages,
                 .partial = partial,
                 .nr_pages_max = MAX_SKB_FRAGS,
                 .ops = &nosteal_pipe_buf_ops,
                 .spd_release = sock_spd_release,
         };
         int ret = 0;
 
         __skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk);
 
         if (spd.nr_pages)
                 ret = splice_to_pipe(pipe, &spd);
 
         return ret;
 }
 EXPORT_SYMBOL_GPL(skb_splice_bits);
 
 static int sendmsg_locked(struct sock *sk, struct msghdr *msg)
 {
         struct socket *sock = sk->sk_socket;
         size_t size = msg_data_left(msg);
 
         if (!sock)
                 return -EINVAL;
 
         if (!sock->ops->sendmsg_locked)
                 return sock_no_sendmsg_locked(sk, msg, size);
 
         return sock->ops->sendmsg_locked(sk, msg, size);
 }
 
 static int sendmsg_unlocked(struct sock *sk, struct msghdr *msg)
 {
         struct socket *sock = sk->sk_socket;
 
         if (!sock)
                 return -EINVAL;
         return sock_sendmsg(sock, msg);
 }
 
 typedef int (*sendmsg_func)(struct sock *sk, struct msghdr *msg);
 static int __skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset,
                            int len, sendmsg_func sendmsg)
 {
         unsigned int orig_len = len;
         struct sk_buff *head = skb;
         unsigned short fragidx;
         int slen, ret;
 
 do_frag_list:
 
         /* Deal with head data */
         while (offset < skb_headlen(skb) && len) {
                 struct kvec kv;
                 struct msghdr msg;
 
                 slen = min_t(int, len, skb_headlen(skb) - offset);
                 kv.iov_base = skb->data + offset;
                 kv.iov_len = slen;
                 memset(&msg, 0, sizeof(msg));
                 msg.msg_flags = MSG_DONTWAIT;
 
                 iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, &kv, 1, slen);
                 ret = INDIRECT_CALL_2(sendmsg, sendmsg_locked,
                                       sendmsg_unlocked, sk, &msg);
                 if (ret <= 0)
                         goto error;
 
                 offset += ret;
                 len -= ret;
         }
 
         /* All the data was skb head? */
         if (!len)
                 goto out;
 
         /* Make offset relative to start of frags */
         offset -= skb_headlen(skb);
 
         /* Find where we are in frag list */
         for (fragidx = 0; fragidx < skb_shinfo(skb)->nr_frags; fragidx++) {
                 skb_frag_t *frag  = &skb_shinfo(skb)->frags[fragidx];
 
                 if (offset < skb_frag_size(frag))
                         break;
 
                 offset -= skb_frag_size(frag);
         }
 
         for (; len && fragidx < skb_shinfo(skb)->nr_frags; fragidx++) {
                 skb_frag_t *frag  = &skb_shinfo(skb)->frags[fragidx];
 
                 slen = min_t(size_t, len, skb_frag_size(frag) - offset);
 
                 while (slen) {
                         struct bio_vec bvec;
                         struct msghdr msg = {
                                 .msg_flags = MSG_SPLICE_PAGES | MSG_DONTWAIT,
                         };
 
                         bvec_set_page(&bvec, skb_frag_page(frag), slen,
                                       skb_frag_off(frag) + offset);
                         iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1,
                                       slen);
 
                         ret = INDIRECT_CALL_2(sendmsg, sendmsg_locked,
                                               sendmsg_unlocked, sk, &msg);
                         if (ret <= 0)
                                 goto error;
 
                         len -= ret;
                         offset += ret;
                         slen -= ret;
                 }
 
                 offset = 0;
         }
 
         if (len) {
                 /* Process any frag lists */
 
                 if (skb == head) {
                         if (skb_has_frag_list(skb)) {
                                 skb = skb_shinfo(skb)->frag_list;
                                 goto do_frag_list;
                         }
                 } else if (skb->next) {
                         skb = skb->next;
                         goto do_frag_list;
                 }
         }
 
 out:
         return orig_len - len;
 
 error:
         return orig_len == len ? ret : orig_len - len;
 }
 
 /* Send skb data on a socket. Socket must be locked. */
 int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
                          int len)
 {
         return __skb_send_sock(sk, skb, offset, len, sendmsg_locked);
 }
 EXPORT_SYMBOL_GPL(skb_send_sock_locked);
 
 /* Send skb data on a socket. Socket must be unlocked. */
 int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len)
 {
         return __skb_send_sock(sk, skb, offset, len, sendmsg_unlocked);
 }
 
 /**
  *      skb_store_bits - store bits from kernel buffer to skb
  *      @skb: destination buffer
  *      @offset: offset in destination
  *      @from: source buffer
  *      @len: number of bytes to copy
  *
  *      Copy the specified number of bytes from the source buffer to the
  *      destination skb.  This function handles all the messy bits of
  *      traversing fragment lists and such.
  */
 
 int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len)
 {
         int start = skb_headlen(skb);
         struct sk_buff *frag_iter;
         int i, copy;
 
         if (offset > (int)skb->len - len)
                 goto fault;
 
         if ((copy = start - offset) > 0) {
                 if (copy > len)
                         copy = len;
                 skb_copy_to_linear_data_offset(skb, offset, from, copy);
                 if ((len -= copy) == 0)
                         return 0;
                 offset += copy;
                 from += copy;
         }
 
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + skb_frag_size(frag);
                 if ((copy = end - offset) > 0) {
                         u32 p_off, p_len, copied;
                         struct page *p;
                         u8 *vaddr;
 
                         if (copy > len)
                                 copy = len;
 
                         skb_frag_foreach_page(frag,
                                               skb_frag_off(frag) + offset - start,
                                               copy, p, p_off, p_len, copied) {
                                 vaddr = kmap_atomic(p);
                                 memcpy(vaddr + p_off, from + copied, p_len);
                                 kunmap_atomic(vaddr);
                         }
 
                         if ((len -= copy) == 0)
                                 return 0;
                         offset += copy;
                         from += copy;
                 }
                 start = end;
         }
 
         skb_walk_frags(skb, frag_iter) {
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + frag_iter->len;
                 if ((copy = end - offset) > 0) {
                         if (copy > len)
                                 copy = len;
                         if (skb_store_bits(frag_iter, offset - start,
                                            from, copy))
                                 goto fault;
                         if ((len -= copy) == 0)
                                 return 0;
                         offset += copy;
                         from += copy;
                 }
                 start = end;
         }
         if (!len)
                 return 0;
 
 fault:
         return -EFAULT;
 }
 EXPORT_SYMBOL(skb_store_bits);
 
 /* Checksum skb data. */
 __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
                       __wsum csum, const struct skb_checksum_ops *ops)
 {
         int start = skb_headlen(skb);
         int i, copy = start - offset;
         struct sk_buff *frag_iter;
         int pos = 0;
 
         /* Checksum header. */
         if (copy > 0) {
                 if (copy > len)
                         copy = len;
                 csum = INDIRECT_CALL_1(ops->update, csum_partial_ext,
                                        skb->data + offset, copy, csum);
                 if ((len -= copy) == 0)
                         return csum;
                 offset += copy;
                 pos     = copy;
         }
 
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int end;
                 skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
                 WARN_ON(start > offset + len);
 
                 end = start + skb_frag_size(frag);
                 if ((copy = end - offset) > 0) {
                         u32 p_off, p_len, copied;
                         struct page *p;
                         __wsum csum2;
                         u8 *vaddr;
 
                         if (copy > len)
                                 copy = len;
 
                         skb_frag_foreach_page(frag,
                                               skb_frag_off(frag) + offset - start,
                                               copy, p, p_off, p_len, copied) {
                                 vaddr = kmap_atomic(p);
                                 csum2 = INDIRECT_CALL_1(ops->update,
                                                         csum_partial_ext,
                                                         vaddr + p_off, p_len, 0);
                                 kunmap_atomic(vaddr);
                                 csum = INDIRECT_CALL_1(ops->combine,
                                                        csum_block_add_ext, csum,
                                                        csum2, pos, p_len);
                                 pos += p_len;
                         }
 
                         if (!(len -= copy))
                                 return csum;
                         offset += copy;
                 }
                 start = end;
         }
 
         skb_walk_frags(skb, frag_iter) {
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + frag_iter->len;
                 if ((copy = end - offset) > 0) {
                         __wsum csum2;
                         if (copy > len)
                                 copy = len;
                         csum2 = __skb_checksum(frag_iter, offset - start,
                                                copy, 0, ops);
                         csum = INDIRECT_CALL_1(ops->combine, csum_block_add_ext,
                                                csum, csum2, pos, copy);
                         if ((len -= copy) == 0)
                                 return csum;
                         offset += copy;
                         pos    += copy;
                 }
                 start = end;
         }
         BUG_ON(len);
 
         return csum;
 }
 EXPORT_SYMBOL(__skb_checksum);
 
 __wsum skb_checksum(const struct sk_buff *skb, int offset,
                     int len, __wsum csum)
 {
         const struct skb_checksum_ops ops = {
                 .update  = csum_partial_ext,
                 .combine = csum_block_add_ext,
         };
 
         return __skb_checksum(skb, offset, len, csum, &ops);
 }
 EXPORT_SYMBOL(skb_checksum);
 
 /* Both of above in one bottle. */
 
 __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
                                     u8 *to, int len)
 {
         int start = skb_headlen(skb);
         int i, copy = start - offset;
         struct sk_buff *frag_iter;
         int pos = 0;
         __wsum csum = 0;
 
         /* Copy header. */
         if (copy > 0) {
                 if (copy > len)
                         copy = len;
                 csum = csum_partial_copy_nocheck(skb->data + offset, to,
                                                  copy);
                 if ((len -= copy) == 0)
                         return csum;
                 offset += copy;
                 to     += copy;
                 pos     = copy;
         }
 
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
                 if ((copy = end - offset) > 0) {
                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
                         u32 p_off, p_len, copied;
                         struct page *p;
                         __wsum csum2;
                         u8 *vaddr;
 
                         if (copy > len)
                                 copy = len;
 
                         skb_frag_foreach_page(frag,
                                               skb_frag_off(frag) + offset - start,
                                               copy, p, p_off, p_len, copied) {
                                 vaddr = kmap_atomic(p);
                                 csum2 = csum_partial_copy_nocheck(vaddr + p_off,
                                                                   to + copied,
                                                                   p_len);
                                 kunmap_atomic(vaddr);
                                 csum = csum_block_add(csum, csum2, pos);
                                 pos += p_len;
                         }
 
                         if (!(len -= copy))
                                 return csum;
                         offset += copy;
                         to     += copy;
                 }
                 start = end;
         }
 
         skb_walk_frags(skb, frag_iter) {
                 __wsum csum2;
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + frag_iter->len;
                 if ((copy = end - offset) > 0) {
                         if (copy > len)
                                 copy = len;
                         csum2 = skb_copy_and_csum_bits(frag_iter,
                                                        offset - start,
                                                        to, copy);
                         csum = csum_block_add(csum, csum2, pos);
                         if ((len -= copy) == 0)
                                 return csum;
                         offset += copy;
                         to     += copy;
                         pos    += copy;
                 }
                 start = end;
         }
         BUG_ON(len);
         return csum;
 }
 EXPORT_SYMBOL(skb_copy_and_csum_bits);
 
 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
 {
         __sum16 sum;
 
         sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
         /* See comments in __skb_checksum_complete(). */
         if (likely(!sum)) {
                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
                     !skb->csum_complete_sw)
                         netdev_rx_csum_fault(skb->dev, skb);
         }
         if (!skb_shared(skb))
                 skb->csum_valid = !sum;
         return sum;
 }
 EXPORT_SYMBOL(__skb_checksum_complete_head);
 
 /* This function assumes skb->csum already holds pseudo header's checksum,
  * which has been changed from the hardware checksum, for example, by
  * __skb_checksum_validate_complete(). And, the original skb->csum must
  * have been validated unsuccessfully for CHECKSUM_COMPLETE case.
  *
  * It returns non-zero if the recomputed checksum is still invalid, otherwise
  * zero. The new checksum is stored back into skb->csum unless the skb is
  * shared.
  */
 __sum16 __skb_checksum_complete(struct sk_buff *skb)
 {
         __wsum csum;
         __sum16 sum;
 
         csum = skb_checksum(skb, 0, skb->len, 0);
 
         sum = csum_fold(csum_add(skb->csum, csum));
         /* This check is inverted, because we already knew the hardware
          * checksum is invalid before calling this function. So, if the
          * re-computed checksum is valid instead, then we have a mismatch
          * between the original skb->csum and skb_checksum(). This means either
          * the original hardware checksum is incorrect or we screw up skb->csum
          * when moving skb->data around.
          */
         if (likely(!sum)) {
                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
                     !skb->csum_complete_sw)
                         netdev_rx_csum_fault(skb->dev, skb);
         }
 
         if (!skb_shared(skb)) {
                 /* Save full packet checksum */
                 skb->csum = csum;
                 skb->ip_summed = CHECKSUM_COMPLETE;
                 skb->csum_complete_sw = 1;
                 skb->csum_valid = !sum;
         }
 
         return sum;
 }
 EXPORT_SYMBOL(__skb_checksum_complete);
 
 static __wsum warn_crc32c_csum_update(const void *buff, int len, __wsum sum)
 {
         net_warn_ratelimited(
                 "%s: attempt to compute crc32c without libcrc32c.ko\n",
                 __func__);
         return 0;
 }
 
 static __wsum warn_crc32c_csum_combine(__wsum csum, __wsum csum2,
                                        int offset, int len)
 {
         net_warn_ratelimited(
                 "%s: attempt to compute crc32c without libcrc32c.ko\n",
                 __func__);
         return 0;
 }
 
 static const struct skb_checksum_ops default_crc32c_ops = {
         .update  = warn_crc32c_csum_update,
         .combine = warn_crc32c_csum_combine,
 };
 
 const struct skb_checksum_ops *crc32c_csum_stub __read_mostly =
         &default_crc32c_ops;
 EXPORT_SYMBOL(crc32c_csum_stub);
 
  /**
  *      skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()
  *      @from: source buffer
  *
  *      Calculates the amount of linear headroom needed in the 'to' skb passed
  *      into skb_zerocopy().
  */
 unsigned int
 skb_zerocopy_headlen(const struct sk_buff *from)
 {
         unsigned int hlen = 0;
 
         if (!from->head_frag ||
             skb_headlen(from) < L1_CACHE_BYTES ||
             skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS) {
                 hlen = skb_headlen(from);
                 if (!hlen)
                         hlen = from->len;
         }
 
         if (skb_has_frag_list(from))
                 hlen = from->len;
 
         return hlen;
 }
 EXPORT_SYMBOL_GPL(skb_zerocopy_headlen);
 
 /**
  *      skb_zerocopy - Zero copy skb to skb
  *      @to: destination buffer
  *      @from: source buffer
  *      @len: number of bytes to copy from source buffer
  *      @hlen: size of linear headroom in destination buffer
  *
  *      Copies up to `len` bytes from `from` to `to` by creating references
  *      to the frags in the source buffer.
  *
  *      The `hlen` as calculated by skb_zerocopy_headlen() specifies the
  *      headroom in the `to` buffer.
  *
  *      Return value:
  *      0: everything is OK
  *      -ENOMEM: couldn't orphan frags of @from due to lack of memory
  *      -EFAULT: skb_copy_bits() found some problem with skb geometry
  */
 int
 skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
 {
         int i, j = 0;
         int plen = 0; /* length of skb->head fragment */
         int ret;
         struct page *page;
         unsigned int offset;
 
         BUG_ON(!from->head_frag && !hlen);
 
         /* dont bother with small payloads */
         if (len <= skb_tailroom(to))
                 return skb_copy_bits(from, 0, skb_put(to, len), len);
 
         if (hlen) {
                 ret = skb_copy_bits(from, 0, skb_put(to, hlen), hlen);
                 if (unlikely(ret))
                         return ret;
                 len -= hlen;
         } else {
                 plen = min_t(int, skb_headlen(from), len);
                 if (plen) {
                         page = virt_to_head_page(from->head);
                         offset = from->data - (unsigned char *)page_address(page);
                         __skb_fill_netmem_desc(to, 0, page_to_netmem(page),
                                                offset, plen);
                         get_page(page);
                         j = 1;
                         len -= plen;
                 }
         }
 
         skb_len_add(to, len + plen);
 
         if (unlikely(skb_orphan_frags(from, GFP_ATOMIC))) {
                 skb_tx_error(from);
                 return -ENOMEM;
         }
         skb_zerocopy_clone(to, from, GFP_ATOMIC);
 
         for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
                 int size;
 
                 if (!len)
                         break;
                 skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
                 size = min_t(int, skb_frag_size(&skb_shinfo(to)->frags[j]),
                                         len);
                 skb_frag_size_set(&skb_shinfo(to)->frags[j], size);
                 len -= size;
                 skb_frag_ref(to, j);
                 j++;
         }
         skb_shinfo(to)->nr_frags = j;
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_zerocopy);
 
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
 {
         __wsum csum;
         long csstart;
 
         if (skb->ip_summed == CHECKSUM_PARTIAL)
                 csstart = skb_checksum_start_offset(skb);
         else
                 csstart = skb_headlen(skb);
 
         BUG_ON(csstart > skb_headlen(skb));
 
         skb_copy_from_linear_data(skb, to, csstart);
 
         csum = 0;
         if (csstart != skb->len)
                 csum = skb_copy_and_csum_bits(skb, csstart, to + csstart,
                                               skb->len - csstart);
 
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 long csstuff = csstart + skb->csum_offset;
 
                 *((__sum16 *)(to + csstuff)) = csum_fold(csum);
         }
 }
 EXPORT_SYMBOL(skb_copy_and_csum_dev);
 
 /**
  *      skb_dequeue - remove from the head of the queue
  *      @list: list to dequeue from
  *
  *      Remove the head of the list. The list lock is taken so the function
  *      may be used safely with other locking list functions. The head item is
  *      returned or %NULL if the list is empty.
  */
 
 struct sk_buff *skb_dequeue(struct sk_buff_head *list)
 {
         unsigned long flags;
         struct sk_buff *result;
 
         spin_lock_irqsave(&list->lock, flags);
         result = __skb_dequeue(list);
         spin_unlock_irqrestore(&list->lock, flags);
         return result;
 }
 EXPORT_SYMBOL(skb_dequeue);
 
 /**
  *      skb_dequeue_tail - remove from the tail of the queue
  *      @list: list to dequeue from
  *
  *      Remove the tail of the list. The list lock is taken so the function
  *      may be used safely with other locking list functions. The tail item is
  *      returned or %NULL if the list is empty.
  */
 struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list)
 {
         unsigned long flags;
         struct sk_buff *result;
 
         spin_lock_irqsave(&list->lock, flags);
         result = __skb_dequeue_tail(list);
         spin_unlock_irqrestore(&list->lock, flags);
         return result;
 }
 EXPORT_SYMBOL(skb_dequeue_tail);
 
 /**
  *      skb_queue_purge_reason - empty a list
  *      @list: list to empty
  *      @reason: drop reason
  *
  *      Delete all buffers on an &sk_buff list. Each buffer is removed from
  *      the list and one reference dropped. This function takes the list
  *      lock and is atomic with respect to other list locking functions.
  */
 void skb_queue_purge_reason(struct sk_buff_head *list,
                             enum skb_drop_reason reason)
 {
         struct sk_buff_head tmp;
         unsigned long flags;
 
         if (skb_queue_empty_lockless(list))
                 return;
 
         __skb_queue_head_init(&tmp);
 
         spin_lock_irqsave(&list->lock, flags);
         skb_queue_splice_init(list, &tmp);
         spin_unlock_irqrestore(&list->lock, flags);
 
         __skb_queue_purge_reason(&tmp, reason);
 }
 EXPORT_SYMBOL(skb_queue_purge_reason);
 
 /**
  *      skb_rbtree_purge - empty a skb rbtree
  *      @root: root of the rbtree to empty
  *      Return value: the sum of truesizes of all purged skbs.
  *
  *      Delete all buffers on an &sk_buff rbtree. Each buffer is removed from
  *      the list and one reference dropped. This function does not take
  *      any lock. Synchronization should be handled by the caller (e.g., TCP
  *      out-of-order queue is protected by the socket lock).
  */
 unsigned int skb_rbtree_purge(struct rb_root *root)
 {
         struct rb_node *p = rb_first(root);
         unsigned int sum = 0;
 
         while (p) {
                 struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
 
                 p = rb_next(p);
                 rb_erase(&skb->rbnode, root);
                 sum += skb->truesize;
                 kfree_skb(skb);
         }
         return sum;
 }
 
 void skb_errqueue_purge(struct sk_buff_head *list)
 {
         struct sk_buff *skb, *next;
         struct sk_buff_head kill;
         unsigned long flags;
 
         __skb_queue_head_init(&kill);
 
         spin_lock_irqsave(&list->lock, flags);
         skb_queue_walk_safe(list, skb, next) {
                 if (SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ZEROCOPY ||
                     SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING)
                         continue;
                 __skb_unlink(skb, list);
                 __skb_queue_tail(&kill, skb);
         }
         spin_unlock_irqrestore(&list->lock, flags);
         __skb_queue_purge(&kill);
 }
 EXPORT_SYMBOL(skb_errqueue_purge);
 
 /**
  *      skb_queue_head - queue a buffer at the list head
  *      @list: list to use
  *      @newsk: buffer to queue
  *
  *      Queue a buffer at the start of the list. This function takes the
  *      list lock and can be used safely with other locking &sk_buff functions
  *      safely.
  *
  *      A buffer cannot be placed on two lists at the same time.
  */
 void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&list->lock, flags);
         __skb_queue_head(list, newsk);
         spin_unlock_irqrestore(&list->lock, flags);
 }
 EXPORT_SYMBOL(skb_queue_head);
 
 /**
  *      skb_queue_tail - queue a buffer at the list tail
  *      @list: list to use
  *      @newsk: buffer to queue
  *
  *      Queue a buffer at the tail of the list. This function takes the
  *      list lock and can be used safely with other locking &sk_buff functions
  *      safely.
  *
  *      A buffer cannot be placed on two lists at the same time.
  */
 void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&list->lock, flags);
         __skb_queue_tail(list, newsk);
         spin_unlock_irqrestore(&list->lock, flags);
 }
 EXPORT_SYMBOL(skb_queue_tail);
 
 /**
  *      skb_unlink      -       remove a buffer from a list
  *      @skb: buffer to remove
  *      @list: list to use
  *
  *      Remove a packet from a list. The list locks are taken and this
  *      function is atomic with respect to other list locked calls
  *
  *      You must know what list the SKB is on.
  */
 void skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&list->lock, flags);
         __skb_unlink(skb, list);
         spin_unlock_irqrestore(&list->lock, flags);
 }
 EXPORT_SYMBOL(skb_unlink);
 
 /**
  *      skb_append      -       append a buffer
  *      @old: buffer to insert after
  *      @newsk: buffer to insert
  *      @list: list to use
  *
  *      Place a packet after a given packet in a list. The list locks are taken
  *      and this function is atomic with respect to other list locked calls.
  *      A buffer cannot be placed on two lists at the same time.
  */
 void skb_append(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&list->lock, flags);
         __skb_queue_after(list, old, newsk);
         spin_unlock_irqrestore(&list->lock, flags);
 }
 EXPORT_SYMBOL(skb_append);
 
 static inline void skb_split_inside_header(struct sk_buff *skb,
                                            struct sk_buff* skb1,
                                            const u32 len, const int pos)
 {
         int i;
 
         skb_copy_from_linear_data_offset(skb, len, skb_put(skb1, pos - len),
                                          pos - len);
         /* And move data appendix as is. */
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                 skb_shinfo(skb1)->frags[i] = skb_shinfo(skb)->frags[i];
 
         skb_shinfo(skb1)->nr_frags = skb_shinfo(skb)->nr_frags;
         skb_shinfo(skb)->nr_frags  = 0;
         skb1->data_len             = skb->data_len;
         skb1->len                  += skb1->data_len;
         skb->data_len              = 0;
         skb->len                   = len;
         skb_set_tail_pointer(skb, len);
 }
 
 static inline void skb_split_no_header(struct sk_buff *skb,
                                        struct sk_buff* skb1,
                                        const u32 len, int pos)
 {
         int i, k = 0;
         const int nfrags = skb_shinfo(skb)->nr_frags;
 
         skb_shinfo(skb)->nr_frags = 0;
         skb1->len                 = skb1->data_len = skb->len - len;
         skb->len                  = len;
         skb->data_len             = len - pos;
 
         for (i = 0; i < nfrags; i++) {
                 int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
 
                 if (pos + size > len) {
                         skb_shinfo(skb1)->frags[k] = skb_shinfo(skb)->frags[i];
 
                         if (pos < len) {
                                 /* Split frag.
                                  * We have two variants in this case:
                                  * 1. Move all the frag to the second
                                  *    part, if it is possible. F.e.
                                  *    this approach is mandatory for TUX,
                                  *    where splitting is expensive.
                                  * 2. Split is accurately. We make this.
                                  */
                                 skb_frag_ref(skb, i);
                                 skb_frag_off_add(&skb_shinfo(skb1)->frags[0], len - pos);
                                 skb_frag_size_sub(&skb_shinfo(skb1)->frags[0], len - pos);
                                 skb_frag_size_set(&skb_shinfo(skb)->frags[i], len - pos);
                                 skb_shinfo(skb)->nr_frags++;
                         }
                         k++;
                 } else
                         skb_shinfo(skb)->nr_frags++;
                 pos += size;
         }
         skb_shinfo(skb1)->nr_frags = k;
 }
 
 /**
  * skb_split - Split fragmented skb to two parts at length len.
  * @skb: the buffer to split
  * @skb1: the buffer to receive the second part
  * @len: new length for skb
  */
 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
 {
         int pos = skb_headlen(skb);
         const int zc_flags = SKBFL_SHARED_FRAG | SKBFL_PURE_ZEROCOPY;
 
         skb_zcopy_downgrade_managed(skb);
 
         skb_shinfo(skb1)->flags |= skb_shinfo(skb)->flags & zc_flags;
         skb_zerocopy_clone(skb1, skb, 0);
         if (len < pos)  /* Split line is inside header. */
                 skb_split_inside_header(skb, skb1, len, pos);
         else            /* Second chunk has no header, nothing to copy. */
                 skb_split_no_header(skb, skb1, len, pos);
 }
 EXPORT_SYMBOL(skb_split);
 
 /* Shifting from/to a cloned skb is a no-go.
  *
  * Caller cannot keep skb_shinfo related pointers past calling here!
  */
 static int skb_prepare_for_shift(struct sk_buff *skb)
 {
         return skb_unclone_keeptruesize(skb, GFP_ATOMIC);
 }
 
 /**
  * skb_shift - Shifts paged data partially from skb to another
  * @tgt: buffer into which tail data gets added
  * @skb: buffer from which the paged data comes from
  * @shiftlen: shift up to this many bytes
  *
  * Attempts to shift up to shiftlen worth of bytes, which may be less than
  * the length of the skb, from skb to tgt. Returns number bytes shifted.
  * It's up to caller to free skb if everything was shifted.
  *
  * If @tgt runs out of frags, the whole operation is aborted.
  *
  * Skb cannot include anything else but paged data while tgt is allowed
  * to have non-paged data as well.
  *
  * TODO: full sized shift could be optimized but that would need
  * specialized skb free'er to handle frags without up-to-date nr_frags.
  */
 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen)
 {
         int from, to, merge, todo;
         skb_frag_t *fragfrom, *fragto;
 
         BUG_ON(shiftlen > skb->len);
 
         if (skb_headlen(skb))
                 return 0;
         if (skb_zcopy(tgt) || skb_zcopy(skb))
                 return 0;
 
         DEBUG_NET_WARN_ON_ONCE(tgt->pp_recycle != skb->pp_recycle);
         DEBUG_NET_WARN_ON_ONCE(skb_cmp_decrypted(tgt, skb));
 
         todo = shiftlen;
         from = 0;
         to = skb_shinfo(tgt)->nr_frags;
         fragfrom = &skb_shinfo(skb)->frags[from];
 
         /* Actual merge is delayed until the point when we know we can
          * commit all, so that we don't have to undo partial changes
          */
         if (!to ||
             !skb_can_coalesce(tgt, to, skb_frag_page(fragfrom),
                               skb_frag_off(fragfrom))) {
                 merge = -1;
         } else {
                 merge = to - 1;
 
                 todo -= skb_frag_size(fragfrom);
                 if (todo < 0) {
                         if (skb_prepare_for_shift(skb) ||
                             skb_prepare_for_shift(tgt))
                                 return 0;
 
                         /* All previous frag pointers might be stale! */
                         fragfrom = &skb_shinfo(skb)->frags[from];
                         fragto = &skb_shinfo(tgt)->frags[merge];
 
                         skb_frag_size_add(fragto, shiftlen);
                         skb_frag_size_sub(fragfrom, shiftlen);
                         skb_frag_off_add(fragfrom, shiftlen);
 
                         goto onlymerged;
                 }
 
                 from++;
         }
 
         /* Skip full, not-fitting skb to avoid expensive operations */
         if ((shiftlen == skb->len) &&
             (skb_shinfo(skb)->nr_frags - from) > (MAX_SKB_FRAGS - to))
                 return 0;
 
         if (skb_prepare_for_shift(skb) || skb_prepare_for_shift(tgt))
                 return 0;
 
         while ((todo > 0) && (from < skb_shinfo(skb)->nr_frags)) {
                 if (to == MAX_SKB_FRAGS)
                         return 0;
 
                 fragfrom = &skb_shinfo(skb)->frags[from];
                 fragto = &skb_shinfo(tgt)->frags[to];
 
                 if (todo >= skb_frag_size(fragfrom)) {
                         *fragto = *fragfrom;
                         todo -= skb_frag_size(fragfrom);
                         from++;
                         to++;
 
                 } else {
                         __skb_frag_ref(fragfrom);
                         skb_frag_page_copy(fragto, fragfrom);
                         skb_frag_off_copy(fragto, fragfrom);
                         skb_frag_size_set(fragto, todo);
 
                         skb_frag_off_add(fragfrom, todo);
                         skb_frag_size_sub(fragfrom, todo);
                         todo = 0;
 
                         to++;
                         break;
                 }
         }
 
         /* Ready to "commit" this state change to tgt */
         skb_shinfo(tgt)->nr_frags = to;
 
         if (merge >= 0) {
                 fragfrom = &skb_shinfo(skb)->frags[0];
                 fragto = &skb_shinfo(tgt)->frags[merge];
 
                 skb_frag_size_add(fragto, skb_frag_size(fragfrom));
                 __skb_frag_unref(fragfrom, skb->pp_recycle);
         }
 
         /* Reposition in the original skb */
         to = 0;
         while (from < skb_shinfo(skb)->nr_frags)
                 skb_shinfo(skb)->frags[to++] = skb_shinfo(skb)->frags[from++];
         skb_shinfo(skb)->nr_frags = to;
 
         BUG_ON(todo > 0 && !skb_shinfo(skb)->nr_frags);
 
 onlymerged:
         /* Most likely the tgt won't ever need its checksum anymore, skb on
          * the other hand might need it if it needs to be resent
          */
         tgt->ip_summed = CHECKSUM_PARTIAL;
         skb->ip_summed = CHECKSUM_PARTIAL;
 
         skb_len_add(skb, -shiftlen);
         skb_len_add(tgt, shiftlen);
 
         return shiftlen;
 }
 
 /**
  * skb_prepare_seq_read - Prepare a sequential read of skb data
  * @skb: the buffer to read
  * @from: lower offset of data to be read
  * @to: upper offset of data to be read
  * @st: state variable
  *
  * Initializes the specified state variable. Must be called before
  * invoking skb_seq_read() for the first time.
  */
 void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,
                           unsigned int to, struct skb_seq_state *st)
 {
         st->lower_offset = from;
         st->upper_offset = to;
         st->root_skb = st->cur_skb = skb;
         st->frag_idx = st->stepped_offset = 0;
         st->frag_data = NULL;
         st->frag_off = 0;
 }
 EXPORT_SYMBOL(skb_prepare_seq_read);
 
 /**
  * skb_seq_read - Sequentially read skb data
  * @consumed: number of bytes consumed by the caller so far
  * @data: destination pointer for data to be returned
  * @st: state variable
  *
  * Reads a block of skb data at @consumed relative to the
  * lower offset specified to skb_prepare_seq_read(). Assigns
  * the head of the data block to @data and returns the length
  * of the block or 0 if the end of the skb data or the upper
  * offset has been reached.
  *
  * The caller is not required to consume all of the data
  * returned, i.e. @consumed is typically set to the number
  * of bytes already consumed and the next call to
  * skb_seq_read() will return the remaining part of the block.
  *
  * Note 1: The size of each block of data returned can be arbitrary,
  *       this limitation is the cost for zerocopy sequential
  *       reads of potentially non linear data.
  *
  * Note 2: Fragment lists within fragments are not implemented
  *       at the moment, state->root_skb could be replaced with
  *       a stack for this purpose.
  */
 unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
                           struct skb_seq_state *st)
 {
         unsigned int block_limit, abs_offset = consumed + st->lower_offset;
         skb_frag_t *frag;
 
         if (unlikely(abs_offset >= st->upper_offset)) {
                 if (st->frag_data) {
                         kunmap_atomic(st->frag_data);
                         st->frag_data = NULL;
                 }
                 return 0;
         }
 
 next_skb:
         block_limit = skb_headlen(st->cur_skb) + st->stepped_offset;
 
         if (abs_offset < block_limit && !st->frag_data) {
                 *data = st->cur_skb->data + (abs_offset - st->stepped_offset);
                 return block_limit - abs_offset;
         }
 
         if (st->frag_idx == 0 && !st->frag_data)
                 st->stepped_offset += skb_headlen(st->cur_skb);
 
         while (st->frag_idx < skb_shinfo(st->cur_skb)->nr_frags) {
                 unsigned int pg_idx, pg_off, pg_sz;
 
                 frag = &skb_shinfo(st->cur_skb)->frags[st->frag_idx];
 
                 pg_idx = 0;
                 pg_off = skb_frag_off(frag);
                 pg_sz = skb_frag_size(frag);
 
                 if (skb_frag_must_loop(skb_frag_page(frag))) {
                         pg_idx = (pg_off + st->frag_off) >> PAGE_SHIFT;
                         pg_off = offset_in_page(pg_off + st->frag_off);
                         pg_sz = min_t(unsigned int, pg_sz - st->frag_off,
                                                     PAGE_SIZE - pg_off);
                 }
 
                 block_limit = pg_sz + st->stepped_offset;
                 if (abs_offset < block_limit) {
                         if (!st->frag_data)
                                 st->frag_data = kmap_atomic(skb_frag_page(frag) + pg_idx);
 
                         *data = (u8 *)st->frag_data + pg_off +
                                 (abs_offset - st->stepped_offset);
 
                         return block_limit - abs_offset;
                 }
 
                 if (st->frag_data) {
                         kunmap_atomic(st->frag_data);
                         st->frag_data = NULL;
                 }
 
                 st->stepped_offset += pg_sz;
                 st->frag_off += pg_sz;
                 if (st->frag_off == skb_frag_size(frag)) {
                         st->frag_off = 0;
                         st->frag_idx++;
                 }
         }
 
         if (st->frag_data) {
                 kunmap_atomic(st->frag_data);
                 st->frag_data = NULL;
         }
 
         if (st->root_skb == st->cur_skb && skb_has_frag_list(st->root_skb)) {
                 st->cur_skb = skb_shinfo(st->root_skb)->frag_list;
                 st->frag_idx = 0;
                 goto next_skb;
         } else if (st->cur_skb->next) {
                 st->cur_skb = st->cur_skb->next;
                 st->frag_idx = 0;
                 goto next_skb;
         }
 
         return 0;
 }
 EXPORT_SYMBOL(skb_seq_read);
 
 /**
  * skb_abort_seq_read - Abort a sequential read of skb data
  * @st: state variable
  *
  * Must be called if skb_seq_read() was not called until it
  * returned 0.
  */
 void skb_abort_seq_read(struct skb_seq_state *st)
 {
         if (st->frag_data)
                 kunmap_atomic(st->frag_data);
 }
 EXPORT_SYMBOL(skb_abort_seq_read);
 
 #define TS_SKB_CB(state)        ((struct skb_seq_state *) &((state)->cb))
 
 static unsigned int skb_ts_get_next_block(unsigned int offset, const u8 **text,
                                           struct ts_config *conf,
                                           struct ts_state *state)
 {
         return skb_seq_read(offset, text, TS_SKB_CB(state));
 }
 
 static void skb_ts_finish(struct ts_config *conf, struct ts_state *state)
 {
         skb_abort_seq_read(TS_SKB_CB(state));
 }
 
 /**
  * skb_find_text - Find a text pattern in skb data
  * @skb: the buffer to look in
  * @from: search offset
  * @to: search limit
  * @config: textsearch configuration
  *
  * Finds a pattern in the skb data according to the specified
  * textsearch configuration. Use textsearch_next() to retrieve
  * subsequent occurrences of the pattern. Returns the offset
  * to the first occurrence or UINT_MAX if no match was found.
  */
 unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
                            unsigned int to, struct ts_config *config)
 {
         unsigned int patlen = config->ops->get_pattern_len(config);
         struct ts_state state;
         unsigned int ret;
 
         BUILD_BUG_ON(sizeof(struct skb_seq_state) > sizeof(state.cb));
 
         config->get_next_block = skb_ts_get_next_block;
         config->finish = skb_ts_finish;
 
         skb_prepare_seq_read(skb, from, to, TS_SKB_CB(&state));
 
         ret = textsearch_find(config, &state);
         return (ret + patlen <= to - from ? ret : UINT_MAX);
 }
 EXPORT_SYMBOL(skb_find_text);
 
 int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
                          int offset, size_t size, size_t max_frags)
 {
         int i = skb_shinfo(skb)->nr_frags;
 
         if (skb_can_coalesce(skb, i, page, offset)) {
                 skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size);
         } else if (i < max_frags) {
                 skb_zcopy_downgrade_managed(skb);
                 get_page(page);
                 skb_fill_page_desc_noacc(skb, i, page, offset, size);
         } else {
                 return -EMSGSIZE;
         }
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_append_pagefrags);
 
 /**
  *      skb_pull_rcsum - pull skb and update receive checksum
  *      @skb: buffer to update
  *      @len: length of data pulled
  *
  *      This function performs an skb_pull on the packet and updates
  *      the CHECKSUM_COMPLETE checksum.  It should be used on
  *      receive path processing instead of skb_pull unless you know
  *      that the checksum difference is zero (e.g., a valid IP header)
  *      or you are setting ip_summed to CHECKSUM_NONE.
  */
 void *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
 {
         unsigned char *data = skb->data;
 
         BUG_ON(len > skb->len);
         __skb_pull(skb, len);
         skb_postpull_rcsum(skb, data, len);
         return skb->data;
 }
 EXPORT_SYMBOL_GPL(skb_pull_rcsum);
 
 static inline skb_frag_t skb_head_frag_to_page_desc(struct sk_buff *frag_skb)
 {
         skb_frag_t head_frag;
         struct page *page;
 
         page = virt_to_head_page(frag_skb->head);
         skb_frag_fill_page_desc(&head_frag, page, frag_skb->data -
                                 (unsigned char *)page_address(page),
                                 skb_headlen(frag_skb));
         return head_frag;
 }
 
 struct sk_buff *skb_segment_list(struct sk_buff *skb,
                                  netdev_features_t features,
                                  unsigned int offset)
 {
         struct sk_buff *list_skb = skb_shinfo(skb)->frag_list;
         unsigned int tnl_hlen = skb_tnl_header_len(skb);
         unsigned int delta_truesize = 0;
         unsigned int delta_len = 0;
         struct sk_buff *tail = NULL;
         struct sk_buff *nskb, *tmp;
         int len_diff, err;
 
         skb_push(skb, -skb_network_offset(skb) + offset);
 
         /* Ensure the head is writeable before touching the shared info */
         err = skb_unclone(skb, GFP_ATOMIC);
         if (err)
                 goto err_linearize;
 
         skb_shinfo(skb)->frag_list = NULL;
 
         while (list_skb) {
                 nskb = list_skb;
                 list_skb = list_skb->next;
 
                 err = 0;
                 delta_truesize += nskb->truesize;
                 if (skb_shared(nskb)) {
                         tmp = skb_clone(nskb, GFP_ATOMIC);
                         if (tmp) {
                                 consume_skb(nskb);
                                 nskb = tmp;
                                 err = skb_unclone(nskb, GFP_ATOMIC);
                         } else {
                                 err = -ENOMEM;
                         }
                 }
 
                 if (!tail)
                         skb->next = nskb;
                 else
                         tail->next = nskb;
 
                 if (unlikely(err)) {
                         nskb->next = list_skb;
                         goto err_linearize;
                 }
 
                 tail = nskb;
 
                 delta_len += nskb->len;
 
                 skb_push(nskb, -skb_network_offset(nskb) + offset);
 
                 skb_release_head_state(nskb);
                 len_diff = skb_network_header_len(nskb) - skb_network_header_len(skb);
                 __copy_skb_header(nskb, skb);
 
                 skb_headers_offset_update(nskb, skb_headroom(nskb) - skb_headroom(skb));
                 nskb->transport_header += len_diff;
                 skb_copy_from_linear_data_offset(skb, -tnl_hlen,
                                                  nskb->data - tnl_hlen,
                                                  offset + tnl_hlen);
 
                 if (skb_needs_linearize(nskb, features) &&
                     __skb_linearize(nskb))
                         goto err_linearize;
         }
 
         skb->truesize = skb->truesize - delta_truesize;
         skb->data_len = skb->data_len - delta_len;
         skb->len = skb->len - delta_len;
 
         skb_gso_reset(skb);
 
         skb->prev = tail;
 
         if (skb_needs_linearize(skb, features) &&
             __skb_linearize(skb))
                 goto err_linearize;
 
         skb_get(skb);
 
         return skb;
 
 err_linearize:
         kfree_skb_list(skb->next);
         skb->next = NULL;
         return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL_GPL(skb_segment_list);
 
 /**
  *      skb_segment - Perform protocol segmentation on skb.
  *      @head_skb: buffer to segment
  *      @features: features for the output path (see dev->features)
  *
  *      This function performs segmentation on the given skb.  It returns
  *      a pointer to the first in a list of new skbs for the segments.
  *      In case of error it returns ERR_PTR(err).
  */
 struct sk_buff *skb_segment(struct sk_buff *head_skb,
                             netdev_features_t features)
 {
         struct sk_buff *segs = NULL;
         struct sk_buff *tail = NULL;
         struct sk_buff *list_skb = skb_shinfo(head_skb)->frag_list;
         unsigned int mss = skb_shinfo(head_skb)->gso_size;
         unsigned int doffset = head_skb->data - skb_mac_header(head_skb);
         unsigned int offset = doffset;
         unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
         unsigned int partial_segs = 0;
         unsigned int headroom;
         unsigned int len = head_skb->len;
         struct sk_buff *frag_skb;
         skb_frag_t *frag;
         __be16 proto;
         bool csum, sg;
         int err = -ENOMEM;
         int i = 0;
         int nfrags, pos;
 
         if ((skb_shinfo(head_skb)->gso_type & SKB_GSO_DODGY) &&
             mss != GSO_BY_FRAGS && mss != skb_headlen(head_skb)) {
                 struct sk_buff *check_skb;
 
                 for (check_skb = list_skb; check_skb; check_skb = check_skb->next) {
                         if (skb_headlen(check_skb) && !check_skb->head_frag) {
                                 /* gso_size is untrusted, and we have a frag_list with
                                  * a linear non head_frag item.
                                  *
                                  * If head_skb's headlen does not fit requested gso_size,
                                  * it means that the frag_list members do NOT terminate
                                  * on exact gso_size boundaries. Hence we cannot perform
                                  * skb_frag_t page sharing. Therefore we must fallback to
                                  * copying the frag_list skbs; we do so by disabling SG.
                                  */
                                 features &= ~NETIF_F_SG;
                                 break;
                         }
                 }
         }
 
         __skb_push(head_skb, doffset);
         proto = skb_network_protocol(head_skb, NULL);
         if (unlikely(!proto))
                 return ERR_PTR(-EINVAL);
 
         sg = !!(features & NETIF_F_SG);
         csum = !!can_checksum_protocol(features, proto);
 
         if (sg && csum && (mss != GSO_BY_FRAGS))  {
                 if (!(features & NETIF_F_GSO_PARTIAL)) {
                         struct sk_buff *iter;
                         unsigned int frag_len;
 
                         if (!list_skb ||
                             !net_gso_ok(features, skb_shinfo(head_skb)->gso_type))
                                 goto normal;
 
                         /* If we get here then all the required
                          * GSO features except frag_list are supported.
                          * Try to split the SKB to multiple GSO SKBs
                          * with no frag_list.
                          * Currently we can do that only when the buffers don't
                          * have a linear part and all the buffers except
                          * the last are of the same length.
                          */
                         frag_len = list_skb->len;
                         skb_walk_frags(head_skb, iter) {
                                 if (frag_len != iter->len && iter->next)
                                         goto normal;
                                 if (skb_headlen(iter) && !iter->head_frag)
                                         goto normal;
 
                                 len -= iter->len;
                         }
 
                         if (len != frag_len)
                                 goto normal;
                 }
 
                 /* GSO partial only requires that we trim off any excess that
                  * doesn't fit into an MSS sized block, so take care of that
                  * now.
                  * Cap len to not accidentally hit GSO_BY_FRAGS.
                  */
                 partial_segs = min(len, GSO_BY_FRAGS - 1) / mss;
                 if (partial_segs > 1)
                         mss *= partial_segs;
                 else
                         partial_segs = 0;
         }
 
 normal:
         headroom = skb_headroom(head_skb);
         pos = skb_headlen(head_skb);
 
         if (skb_orphan_frags(head_skb, GFP_ATOMIC))
                 return ERR_PTR(-ENOMEM);
 
         nfrags = skb_shinfo(head_skb)->nr_frags;
         frag = skb_shinfo(head_skb)->frags;
         frag_skb = head_skb;
 
         do {
                 struct sk_buff *nskb;
                 skb_frag_t *nskb_frag;
                 int hsize;
                 int size;
 
                 if (unlikely(mss == GSO_BY_FRAGS)) {
                         len = list_skb->len;
                 } else {
                         len = head_skb->len - offset;
                         if (len > mss)
                                 len = mss;
                 }
 
                 hsize = skb_headlen(head_skb) - offset;
 
                 if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) &&
                     (skb_headlen(list_skb) == len || sg)) {
                         BUG_ON(skb_headlen(list_skb) > len);
 
                         nskb = skb_clone(list_skb, GFP_ATOMIC);
                         if (unlikely(!nskb))
                                 goto err;
 
                         i = 0;
                         nfrags = skb_shinfo(list_skb)->nr_frags;
                         frag = skb_shinfo(list_skb)->frags;
                         frag_skb = list_skb;
                         pos += skb_headlen(list_skb);
 
                         while (pos < offset + len) {
                                 BUG_ON(i >= nfrags);
 
                                 size = skb_frag_size(frag);
                                 if (pos + size > offset + len)
                                         break;
 
                                 i++;
                                 pos += size;
                                 frag++;
                         }
 
                         list_skb = list_skb->next;
 
                         if (unlikely(pskb_trim(nskb, len))) {
                                 kfree_skb(nskb);
                                 goto err;
                         }
 
                         hsize = skb_end_offset(nskb);
                         if (skb_cow_head(nskb, doffset + headroom)) {
                                 kfree_skb(nskb);
                                 goto err;
                         }
 
                         nskb->truesize += skb_end_offset(nskb) - hsize;
                         skb_release_head_state(nskb);
                         __skb_push(nskb, doffset);
                 } else {
                         if (hsize < 0)
                                 hsize = 0;
                         if (hsize > len || !sg)
                                 hsize = len;
 
                         nskb = __alloc_skb(hsize + doffset + headroom,
                                            GFP_ATOMIC, skb_alloc_rx_flag(head_skb),
                                            NUMA_NO_NODE);
 
                         if (unlikely(!nskb))
                                 goto err;
 
                         skb_reserve(nskb, headroom);
                         __skb_put(nskb, doffset);
                 }
 
                 if (segs)
                         tail->next = nskb;
                 else
                         segs = nskb;
                 tail = nskb;
 
                 __copy_skb_header(nskb, head_skb);
 
                 skb_headers_offset_update(nskb, skb_headroom(nskb) - headroom);
                 skb_reset_mac_len(nskb);
 
                 skb_copy_from_linear_data_offset(head_skb, -tnl_hlen,
                                                  nskb->data - tnl_hlen,
                                                  doffset + tnl_hlen);
 
                 if (nskb->len == len + doffset)
                         goto perform_csum_check;
 
                 if (!sg) {
                         if (!csum) {
                                 if (!nskb->remcsum_offload)
                                         nskb->ip_summed = CHECKSUM_NONE;
                                 SKB_GSO_CB(nskb)->csum =
                                         skb_copy_and_csum_bits(head_skb, offset,
                                                                skb_put(nskb,
                                                                        len),
                                                                len);
                                 SKB_GSO_CB(nskb)->csum_start =
                                         skb_headroom(nskb) + doffset;
                         } else {
                                 if (skb_copy_bits(head_skb, offset, skb_put(nskb, len), len))
                                         goto err;
                         }
                         continue;
                 }
 
                 nskb_frag = skb_shinfo(nskb)->frags;
 
                 skb_copy_from_linear_data_offset(head_skb, offset,
                                                  skb_put(nskb, hsize), hsize);
 
                 skb_shinfo(nskb)->flags |= skb_shinfo(head_skb)->flags &
                                            SKBFL_SHARED_FRAG;
 
                 if (skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))
                         goto err;
 
                 while (pos < offset + len) {
                         if (i >= nfrags) {
                                 if (skb_orphan_frags(list_skb, GFP_ATOMIC) ||
                                     skb_zerocopy_clone(nskb, list_skb,
                                                        GFP_ATOMIC))
                                         goto err;
 
                                 i = 0;
                                 nfrags = skb_shinfo(list_skb)->nr_frags;
                                 frag = skb_shinfo(list_skb)->frags;
                                 frag_skb = list_skb;
                                 if (!skb_headlen(list_skb)) {
                                         BUG_ON(!nfrags);
                                 } else {
                                         BUG_ON(!list_skb->head_frag);
 
                                         /* to make room for head_frag. */
                                         i--;
                                         frag--;
                                 }
 
                                 list_skb = list_skb->next;
                         }
 
                         if (unlikely(skb_shinfo(nskb)->nr_frags >=
                                      MAX_SKB_FRAGS)) {
                                 net_warn_ratelimited(
                                         "skb_segment: too many frags: %u %u\n",
                                         pos, mss);
                                 err = -EINVAL;
                                 goto err;
                         }
 
                         *nskb_frag = (i < 0) ? skb_head_frag_to_page_desc(frag_skb) : *frag;
                         __skb_frag_ref(nskb_frag);
                         size = skb_frag_size(nskb_frag);
 
                         if (pos < offset) {
                                 skb_frag_off_add(nskb_frag, offset - pos);
                                 skb_frag_size_sub(nskb_frag, offset - pos);
                         }
 
                         skb_shinfo(nskb)->nr_frags++;
 
                         if (pos + size <= offset + len) {
                                 i++;
                                 frag++;
                                 pos += size;
                         } else {
                                 skb_frag_size_sub(nskb_frag, pos + size - (offset + len));
                                 goto skip_fraglist;
                         }
 
                         nskb_frag++;
                 }
 
 skip_fraglist:
                 nskb->data_len = len - hsize;
                 nskb->len += nskb->data_len;
                 nskb->truesize += nskb->data_len;
 
 perform_csum_check:
                 if (!csum) {
                         if (skb_has_shared_frag(nskb) &&
                             __skb_linearize(nskb))
                                 goto err;
 
                         if (!nskb->remcsum_offload)
                                 nskb->ip_summed = CHECKSUM_NONE;
                         SKB_GSO_CB(nskb)->csum =
                                 skb_checksum(nskb, doffset,
                                              nskb->len - doffset, 0);
                         SKB_GSO_CB(nskb)->csum_start =
                                 skb_headroom(nskb) + doffset;
                 }
         } while ((offset += len) < head_skb->len);
 
         /* Some callers want to get the end of the list.
          * Put it in segs->prev to avoid walking the list.
          * (see validate_xmit_skb_list() for example)
          */
         segs->prev = tail;
 
         if (partial_segs) {
                 struct sk_buff *iter;
                 int type = skb_shinfo(head_skb)->gso_type;
                 unsigned short gso_size = skb_shinfo(head_skb)->gso_size;
 
                 /* Update type to add partial and then remove dodgy if set */
                 type |= (features & NETIF_F_GSO_PARTIAL) / NETIF_F_GSO_PARTIAL * SKB_GSO_PARTIAL;
                 type &= ~SKB_GSO_DODGY;
 
                 /* Update GSO info and prepare to start updating headers on
                  * our way back down the stack of protocols.
                  */
                 for (iter = segs; iter; iter = iter->next) {
                         skb_shinfo(iter)->gso_size = gso_size;
                         skb_shinfo(iter)->gso_segs = partial_segs;
                         skb_shinfo(iter)->gso_type = type;
                         SKB_GSO_CB(iter)->data_offset = skb_headroom(iter) + doffset;
                 }
 
                 if (tail->len - doffset <= gso_size)
                         skb_shinfo(tail)->gso_size = 0;
                 else if (tail != segs)
                         skb_shinfo(tail)->gso_segs = DIV_ROUND_UP(tail->len - doffset, gso_size);
         }
 
         /* Following permits correct backpressure, for protocols
          * using skb_set_owner_w().
          * Idea is to tranfert ownership from head_skb to last segment.
          */
         if (head_skb->destructor == sock_wfree) {
                 swap(tail->truesize, head_skb->truesize);
                 swap(tail->destructor, head_skb->destructor);
                 swap(tail->sk, head_skb->sk);
         }
         return segs;
 
 err:
         kfree_skb_list(segs);
         return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(skb_segment);
 
 #ifdef CONFIG_SKB_EXTENSIONS
 #define SKB_EXT_ALIGN_VALUE     8
 #define SKB_EXT_CHUNKSIZEOF(x)  (ALIGN((sizeof(x)), SKB_EXT_ALIGN_VALUE) / SKB_EXT_ALIGN_VALUE)
 
 static const u8 skb_ext_type_len[] = {
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
         [SKB_EXT_BRIDGE_NF] = SKB_EXT_CHUNKSIZEOF(struct nf_bridge_info),
 #endif
 #ifdef CONFIG_XFRM
         [SKB_EXT_SEC_PATH] = SKB_EXT_CHUNKSIZEOF(struct sec_path),
 #endif
 #if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
         [TC_SKB_EXT] = SKB_EXT_CHUNKSIZEOF(struct tc_skb_ext),
 #endif
 #if IS_ENABLED(CONFIG_MPTCP)
         [SKB_EXT_MPTCP] = SKB_EXT_CHUNKSIZEOF(struct mptcp_ext),
 #endif
 #if IS_ENABLED(CONFIG_MCTP_FLOWS)
         [SKB_EXT_MCTP] = SKB_EXT_CHUNKSIZEOF(struct mctp_flow),
 #endif
 };
 
 static __always_inline unsigned int skb_ext_total_length(void)
 {
         unsigned int l = SKB_EXT_CHUNKSIZEOF(struct skb_ext);
         int i;
 
         for (i = 0; i < ARRAY_SIZE(skb_ext_type_len); i++)
                 l += skb_ext_type_len[i];
 
         return l;
 }
 
 static void skb_extensions_init(void)
 {
         BUILD_BUG_ON(SKB_EXT_NUM >= 8);
 #if !IS_ENABLED(CONFIG_KCOV_INSTRUMENT_ALL)
         BUILD_BUG_ON(skb_ext_total_length() > 255);
 #endif
 
         skbuff_ext_cache = kmem_cache_create("skbuff_ext_cache",
                                              SKB_EXT_ALIGN_VALUE * skb_ext_total_length(),
                                              0,
                                              SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                                              NULL);
 }
 #else
 static void skb_extensions_init(void) {}
 #endif
 
 /* The SKB kmem_cache slab is critical for network performance.  Never
  * merge/alias the slab with similar sized objects.  This avoids fragmentation
  * that hurts performance of kmem_cache_{alloc,free}_bulk APIs.
  */
 #ifndef CONFIG_SLUB_TINY
 #define FLAG_SKB_NO_MERGE       SLAB_NO_MERGE
 #else /* CONFIG_SLUB_TINY - simple loop in kmem_cache_alloc_bulk */
 #define FLAG_SKB_NO_MERGE       0
 #endif
 
 void __init skb_init(void)
 {
         net_hotdata.skbuff_cache = kmem_cache_create_usercopy("skbuff_head_cache",
                                               sizeof(struct sk_buff),
                                               0,
                                               SLAB_HWCACHE_ALIGN|SLAB_PANIC|
                                                 FLAG_SKB_NO_MERGE,
                                               offsetof(struct sk_buff, cb),
                                               sizeof_field(struct sk_buff, cb),
                                               NULL);
         net_hotdata.skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
                                                 sizeof(struct sk_buff_fclones),
                                                 0,
                                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                                                 NULL);
         /* usercopy should only access first SKB_SMALL_HEAD_HEADROOM bytes.
          * struct skb_shared_info is located at the end of skb->head,
          * and should not be copied to/from user.
          */
         net_hotdata.skb_small_head_cache = kmem_cache_create_usercopy("skbuff_small_head",
                                                 SKB_SMALL_HEAD_CACHE_SIZE,
                                                 0,
                                                 SLAB_HWCACHE_ALIGN | SLAB_PANIC,
                                                 0,
                                                 SKB_SMALL_HEAD_HEADROOM,
                                                 NULL);
         skb_extensions_init();
 }
 
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len,
                unsigned int recursion_level)
 {
         int start = skb_headlen(skb);
         int i, copy = start - offset;
         struct sk_buff *frag_iter;
         int elt = 0;
 
         if (unlikely(recursion_level >= 24))
                 return -EMSGSIZE;
 
         if (copy > 0) {
                 if (copy > len)
                         copy = len;
                 sg_set_buf(sg, skb->data + offset, copy);
                 elt++;
                 if ((len -= copy) == 0)
                         return elt;
                 offset += copy;
         }
 
         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                 int end;
 
                 WARN_ON(start > offset + len);
 
                 end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
                 if ((copy = end - offset) > 0) {
                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
                         if (unlikely(elt && sg_is_last(&sg[elt - 1])))
                                 return -EMSGSIZE;
 
                         if (copy > len)
                                 copy = len;
                         sg_set_page(&sg[elt], skb_frag_page(frag), copy,
                                     skb_frag_off(frag) + offset - start);
                         elt++;
                         if (!(len -= copy))
                                 return elt;
                         offset += copy;
                 }
                 start = end;
         }
 
         skb_walk_frags(skb, frag_iter) {
                 int end, ret;
 
                 WARN_ON(start > offset + len);
 
                 end = start + frag_iter->len;
                 if ((copy = end - offset) > 0) {
                         if (unlikely(elt && sg_is_last(&sg[elt - 1])))
                                 return -EMSGSIZE;
 
                         if (copy > len)
                                 copy = len;
                         ret = __skb_to_sgvec(frag_iter, sg+elt, offset - start,
                                               copy, recursion_level + 1);
                         if (unlikely(ret < 0))
                                 return ret;
                         elt += ret;
                         if ((len -= copy) == 0)
                                 return elt;
                         offset += copy;
                 }
                 start = end;
         }
         BUG_ON(len);
         return elt;
 }
 
 /**
  *      skb_to_sgvec - Fill a scatter-gather list from a socket buffer
  *      @skb: Socket buffer containing the buffers to be mapped
  *      @sg: The scatter-gather list to map into
  *      @offset: The offset into the buffer's contents to start mapping
  *      @len: Length of buffer space to be mapped
  *
  *      Fill the specified scatter-gather list with mappings/pointers into a
  *      region of the buffer space attached to a socket buffer. Returns either
  *      the number of scatterlist items used, or -EMSGSIZE if the contents
  *      could not fit.
  */
 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 {
         int nsg = __skb_to_sgvec(skb, sg, offset, len, 0);
 
         if (nsg <= 0)
                 return nsg;
 
         sg_mark_end(&sg[nsg - 1]);
 
         return nsg;
 }
 EXPORT_SYMBOL_GPL(skb_to_sgvec);
 
 /* As compared with skb_to_sgvec, skb_to_sgvec_nomark only map skb to given
  * sglist without mark the sg which contain last skb data as the end.
  * So the caller can mannipulate sg list as will when padding new data after
  * the first call without calling sg_unmark_end to expend sg list.
  *
  * Scenario to use skb_to_sgvec_nomark:
  * 1. sg_init_table
  * 2. skb_to_sgvec_nomark(payload1)
  * 3. skb_to_sgvec_nomark(payload2)
  *
  * This is equivalent to:
  * 1. sg_init_table
  * 2. skb_to_sgvec(payload1)
  * 3. sg_unmark_end
  * 4. skb_to_sgvec(payload2)
  *
  * When mapping mutilple payload conditionally, skb_to_sgvec_nomark
  * is more preferable.
  */
 int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
                         int offset, int len)
 {
         return __skb_to_sgvec(skb, sg, offset, len, 0);
 }
 EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark);
 
 
 
 /**
  *      skb_cow_data - Check that a socket buffer's data buffers are writable
  *      @skb: The socket buffer to check.
  *      @tailbits: Amount of trailing space to be added
  *      @trailer: Returned pointer to the skb where the @tailbits space begins
  *
  *      Make sure that the data buffers attached to a socket buffer are
  *      writable. If they are not, private copies are made of the data buffers
  *      and the socket buffer is set to use these instead.
  *
  *      If @tailbits is given, make sure that there is space to write @tailbits
  *      bytes of data beyond current end of socket buffer.  @trailer will be
  *      set to point to the skb in which this space begins.
  *
  *      The number of scatterlist elements required to completely map the
  *      COW'd and extended socket buffer will be returned.
  */
 int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer)
 {
         int copyflag;
         int elt;
         struct sk_buff *skb1, **skb_p;
 
         /* If skb is cloned or its head is paged, reallocate
          * head pulling out all the pages (pages are considered not writable
          * at the moment even if they are anonymous).
          */
         if ((skb_cloned(skb) || skb_shinfo(skb)->nr_frags) &&
             !__pskb_pull_tail(skb, __skb_pagelen(skb)))
                 return -ENOMEM;
 
         /* Easy case. Most of packets will go this way. */
         if (!skb_has_frag_list(skb)) {
                 /* A little of trouble, not enough of space for trailer.
                  * This should not happen, when stack is tuned to generate
                  * good frames. OK, on miss we reallocate and reserve even more
                  * space, 128 bytes is fair. */
 
                 if (skb_tailroom(skb) < tailbits &&
                     pskb_expand_head(skb, 0, tailbits-skb_tailroom(skb)+128, GFP_ATOMIC))
                         return -ENOMEM;
 
                 /* Voila! */
                 *trailer = skb;
                 return 1;
         }
 
         /* Misery. We are in troubles, going to mincer fragments... */
 
         elt = 1;
         skb_p = &skb_shinfo(skb)->frag_list;
         copyflag = 0;
 
         while ((skb1 = *skb_p) != NULL) {
                 int ntail = 0;
 
                 /* The fragment is partially pulled by someone,
                  * this can happen on input. Copy it and everything
                  * after it. */
 
                 if (skb_shared(skb1))
                         copyflag = 1;
 
                 /* If the skb is the last, worry about trailer. */
 
                 if (skb1->next == NULL && tailbits) {
                         if (skb_shinfo(skb1)->nr_frags ||
                             skb_has_frag_list(skb1) ||
                             skb_tailroom(skb1) < tailbits)
                                 ntail = tailbits + 128;
                 }
 
                 if (copyflag ||
                     skb_cloned(skb1) ||
                     ntail ||
                     skb_shinfo(skb1)->nr_frags ||
                     skb_has_frag_list(skb1)) {
                         struct sk_buff *skb2;
 
                         /* Fuck, we are miserable poor guys... */
                         if (ntail == 0)
                                 skb2 = skb_copy(skb1, GFP_ATOMIC);
                         else
                                 skb2 = skb_copy_expand(skb1,
                                                        skb_headroom(skb1),
                                                        ntail,
                                                        GFP_ATOMIC);
                         if (unlikely(skb2 == NULL))
                                 return -ENOMEM;
 
                         if (skb1->sk)
                                 skb_set_owner_w(skb2, skb1->sk);
 
                         /* Looking around. Are we still alive?
                          * OK, link new skb, drop old one */
 
                         skb2->next = skb1->next;
                         *skb_p = skb2;
                         kfree_skb(skb1);
                         skb1 = skb2;
                 }
                 elt++;
                 *trailer = skb1;
                 skb_p = &skb1->next;
         }
 
         return elt;
 }
 EXPORT_SYMBOL_GPL(skb_cow_data);
 
 static void sock_rmem_free(struct sk_buff *skb)
 {
         struct sock *sk = skb->sk;
 
         atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
 }
 
 static void skb_set_err_queue(struct sk_buff *skb)
 {
         /* pkt_type of skbs received on local sockets is never PACKET_OUTGOING.
          * So, it is safe to (mis)use it to mark skbs on the error queue.
          */
         skb->pkt_type = PACKET_OUTGOING;
         BUILD_BUG_ON(PACKET_OUTGOING == 0);
 }
 
 /*
  * Note: We dont mem charge error packets (no sk_forward_alloc changes)
  */
 int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
 {
         if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
             (unsigned int)READ_ONCE(sk->sk_rcvbuf))
                 return -ENOMEM;
 
         skb_orphan(skb);
         skb->sk = sk;
         skb->destructor = sock_rmem_free;
         atomic_add(skb->truesize, &sk->sk_rmem_alloc);
         skb_set_err_queue(skb);
 
         /* before exiting rcu section, make sure dst is refcounted */
         skb_dst_force(skb);
 
         skb_queue_tail(&sk->sk_error_queue, skb);
         if (!sock_flag(sk, SOCK_DEAD))
                 sk_error_report(sk);
         return 0;
 }
 EXPORT_SYMBOL(sock_queue_err_skb);
 
 static bool is_icmp_err_skb(const struct sk_buff *skb)
 {
         return skb && (SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
                        SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP6);
 }
 
 struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
 {
         struct sk_buff_head *q = &sk->sk_error_queue;
         struct sk_buff *skb, *skb_next = NULL;
         bool icmp_next = false;
         unsigned long flags;
 
         if (skb_queue_empty_lockless(q))
                 return NULL;
 
         spin_lock_irqsave(&q->lock, flags);
         skb = __skb_dequeue(q);
         if (skb && (skb_next = skb_peek(q))) {
                 icmp_next = is_icmp_err_skb(skb_next);
                 if (icmp_next)
                         sk->sk_err = SKB_EXT_ERR(skb_next)->ee.ee_errno;
         }
         spin_unlock_irqrestore(&q->lock, flags);
 
         if (is_icmp_err_skb(skb) && !icmp_next)
                 sk->sk_err = 0;
 
         if (skb_next)
                 sk_error_report(sk);
 
         return skb;
 }
 EXPORT_SYMBOL(sock_dequeue_err_skb);
 
 /**
  * skb_clone_sk - create clone of skb, and take reference to socket
  * @skb: the skb to clone
  *
  * This function creates a clone of a buffer that holds a reference on
  * sk_refcnt.  Buffers created via this function are meant to be
  * returned using sock_queue_err_skb, or free via kfree_skb.
  *
  * When passing buffers allocated with this function to sock_queue_err_skb
  * it is necessary to wrap the call with sock_hold/sock_put in order to
  * prevent the socket from being released prior to being enqueued on
  * the sk_error_queue.
  */
 struct sk_buff *skb_clone_sk(struct sk_buff *skb)
 {
         struct sock *sk = skb->sk;
         struct sk_buff *clone;
 
         if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
                 return NULL;
 
         clone = skb_clone(skb, GFP_ATOMIC);
         if (!clone) {
                 sock_put(sk);
                 return NULL;
         }
 
         clone->sk = sk;
         clone->destructor = sock_efree;
 
         return clone;
 }
 EXPORT_SYMBOL(skb_clone_sk);
 
 static void __skb_complete_tx_timestamp(struct sk_buff *skb,
                                         struct sock *sk,
                                         int tstype,
                                         bool opt_stats)
 {
         struct sock_exterr_skb *serr;
         int err;
 
         BUILD_BUG_ON(sizeof(struct sock_exterr_skb) > sizeof(skb->cb));
 
         serr = SKB_EXT_ERR(skb);
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = ENOMSG;
         serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
         serr->ee.ee_info = tstype;
         serr->opt_stats = opt_stats;
         serr->header.h4.iif = skb->dev ? skb->dev->ifindex : 0;
         if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID) {
                 serr->ee.ee_data = skb_shinfo(skb)->tskey;
                 if (sk_is_tcp(sk))
                         serr->ee.ee_data -= atomic_read(&sk->sk_tskey);
         }
 
         err = sock_queue_err_skb(sk, skb);
 
         if (err)
                 kfree_skb(skb);
 }
 
 static bool skb_may_tx_timestamp(struct sock *sk, bool tsonly)
 {
         bool ret;
 
         if (likely(READ_ONCE(sysctl_tstamp_allow_data) || tsonly))
                 return true;
 
         read_lock_bh(&sk->sk_callback_lock);
         ret = sk->sk_socket && sk->sk_socket->file &&
               file_ns_capable(sk->sk_socket->file, &init_user_ns, CAP_NET_RAW);
         read_unlock_bh(&sk->sk_callback_lock);
         return ret;
 }
 
 void skb_complete_tx_timestamp(struct sk_buff *skb,
                                struct skb_shared_hwtstamps *hwtstamps)
 {
         struct sock *sk = skb->sk;
 
         if (!skb_may_tx_timestamp(sk, false))
                 goto err;
 
         /* Take a reference to prevent skb_orphan() from freeing the socket,
          * but only if the socket refcount is not zero.
          */
         if (likely(refcount_inc_not_zero(&sk->sk_refcnt))) {
                 *skb_hwtstamps(skb) = *hwtstamps;
                 __skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND, false);
                 sock_put(sk);
                 return;
         }
 
 err:
         kfree_skb(skb);
 }
 EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
 
 void __skb_tstamp_tx(struct sk_buff *orig_skb,
                      const struct sk_buff *ack_skb,
                      struct skb_shared_hwtstamps *hwtstamps,
                      struct sock *sk, int tstype)
 {
         struct sk_buff *skb;
         bool tsonly, opt_stats = false;
         u32 tsflags;
 
         if (!sk)
                 return;
 
         tsflags = READ_ONCE(sk->sk_tsflags);
         if (!hwtstamps && !(tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
             skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
                 return;
 
         tsonly = tsflags & SOF_TIMESTAMPING_OPT_TSONLY;
         if (!skb_may_tx_timestamp(sk, tsonly))
                 return;
 
         if (tsonly) {
 #ifdef CONFIG_INET
                 if ((tsflags & SOF_TIMESTAMPING_OPT_STATS) &&
                     sk_is_tcp(sk)) {
                         skb = tcp_get_timestamping_opt_stats(sk, orig_skb,
                                                              ack_skb);
                         opt_stats = true;
                 } else
 #endif
                         skb = alloc_skb(0, GFP_ATOMIC);
         } else {
                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 
                 if (skb_orphan_frags_rx(skb, GFP_ATOMIC)) {
                         kfree_skb(skb);
                         return;
                 }
         }
         if (!skb)
                 return;
 
         if (tsonly) {
                 skb_shinfo(skb)->tx_flags |= skb_shinfo(orig_skb)->tx_flags &
                                              SKBTX_ANY_TSTAMP;
                 skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
         }
 
         if (hwtstamps)
                 *skb_hwtstamps(skb) = *hwtstamps;
         else
                 __net_timestamp(skb);
 
         __skb_complete_tx_timestamp(skb, sk, tstype, opt_stats);
 }
 EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
 
 void skb_tstamp_tx(struct sk_buff *orig_skb,
                    struct skb_shared_hwtstamps *hwtstamps)
 {
         return __skb_tstamp_tx(orig_skb, NULL, hwtstamps, orig_skb->sk,
                                SCM_TSTAMP_SND);
 }
 EXPORT_SYMBOL_GPL(skb_tstamp_tx);
 
 #ifdef CONFIG_WIRELESS
 void skb_complete_wifi_ack(struct sk_buff *skb, bool acked)
 {
         struct sock *sk = skb->sk;
         struct sock_exterr_skb *serr;
         int err = 1;
 
         skb->wifi_acked_valid = 1;
         skb->wifi_acked = acked;
 
         serr = SKB_EXT_ERR(skb);
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = ENOMSG;
         serr->ee.ee_origin = SO_EE_ORIGIN_TXSTATUS;
 
         /* Take a reference to prevent skb_orphan() from freeing the socket,
          * but only if the socket refcount is not zero.
          */
         if (likely(refcount_inc_not_zero(&sk->sk_refcnt))) {
                 err = sock_queue_err_skb(sk, skb);
                 sock_put(sk);
         }
         if (err)
                 kfree_skb(skb);
 }
 EXPORT_SYMBOL_GPL(skb_complete_wifi_ack);
 #endif /* CONFIG_WIRELESS */
 
 /**
  * skb_partial_csum_set - set up and verify partial csum values for packet
  * @skb: the skb to set
  * @start: the number of bytes after skb->data to start checksumming.
  * @off: the offset from start to place the checksum.
  *
  * For untrusted partially-checksummed packets, we need to make sure the values
  * for skb->csum_start and skb->csum_offset are valid so we don't oops.
  *
  * This function checks and sets those values and skb->ip_summed: if this
  * returns false you should drop the packet.
  */
 bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off)
 {
         u32 csum_end = (u32)start + (u32)off + sizeof(__sum16);
         u32 csum_start = skb_headroom(skb) + (u32)start;
 
         if (unlikely(csum_start >= U16_MAX || csum_end > skb_headlen(skb))) {
                 net_warn_ratelimited("bad partial csum: csum=%u/%u headroom=%u headlen=%u\n",
                                      start, off, skb_headroom(skb), skb_headlen(skb));
                 return false;
         }
         skb->ip_summed = CHECKSUM_PARTIAL;
         skb->csum_start = csum_start;
         skb->csum_offset = off;
         skb->transport_header = csum_start;
         return true;
 }
 EXPORT_SYMBOL_GPL(skb_partial_csum_set);
 
 static int skb_maybe_pull_tail(struct sk_buff *skb, unsigned int len,
                                unsigned int max)
 {
         if (skb_headlen(skb) >= len)
                 return 0;
 
         /* If we need to pullup then pullup to the max, so we
          * won't need to do it again.
          */
         if (max > skb->len)
                 max = skb->len;
 
         if (__pskb_pull_tail(skb, max - skb_headlen(skb)) == NULL)
                 return -ENOMEM;
 
         if (skb_headlen(skb) < len)
                 return -EPROTO;
 
         return 0;
 }
 
 #define MAX_TCP_HDR_LEN (15 * 4)
 
 static __sum16 *skb_checksum_setup_ip(struct sk_buff *skb,
                                       typeof(IPPROTO_IP) proto,
                                       unsigned int off)
 {
         int err;
 
         switch (proto) {
         case IPPROTO_TCP:
                 err = skb_maybe_pull_tail(skb, off + sizeof(struct tcphdr),
                                           off + MAX_TCP_HDR_LEN);
                 if (!err && !skb_partial_csum_set(skb, off,
                                                   offsetof(struct tcphdr,
                                                            check)))
                         err = -EPROTO;
                 return err ? ERR_PTR(err) : &tcp_hdr(skb)->check;
 
         case IPPROTO_UDP:
                 err = skb_maybe_pull_tail(skb, off + sizeof(struct udphdr),
                                           off + sizeof(struct udphdr));
                 if (!err && !skb_partial_csum_set(skb, off,
                                                   offsetof(struct udphdr,
                                                            check)))
                         err = -EPROTO;
                 return err ? ERR_PTR(err) : &udp_hdr(skb)->check;
         }
 
         return ERR_PTR(-EPROTO);
 }
 
 /* This value should be large enough to cover a tagged ethernet header plus
  * maximally sized IP and TCP or UDP headers.
  */
 #define MAX_IP_HDR_LEN 128
 
 static int skb_checksum_setup_ipv4(struct sk_buff *skb, bool recalculate)
 {
         unsigned int off;
         bool fragment;
         __sum16 *csum;
         int err;
 
         fragment = false;
 
         err = skb_maybe_pull_tail(skb,
                                   sizeof(struct iphdr),
                                   MAX_IP_HDR_LEN);
         if (err < 0)
                 goto out;
 
         if (ip_is_fragment(ip_hdr(skb)))
                 fragment = true;
 
         off = ip_hdrlen(skb);
 
         err = -EPROTO;
 
         if (fragment)
                 goto out;
 
         csum = skb_checksum_setup_ip(skb, ip_hdr(skb)->protocol, off);
         if (IS_ERR(csum))
                 return PTR_ERR(csum);
 
         if (recalculate)
                 *csum = ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
                                            ip_hdr(skb)->daddr,
                                            skb->len - off,
                                            ip_hdr(skb)->protocol, 0);
         err = 0;
 
 out:
         return err;
 }
 
 /* This value should be large enough to cover a tagged ethernet header plus
  * an IPv6 header, all options, and a maximal TCP or UDP header.
  */
 #define MAX_IPV6_HDR_LEN 256
 
 #define OPT_HDR(type, skb, off) \
         (type *)(skb_network_header(skb) + (off))
 
 static int skb_checksum_setup_ipv6(struct sk_buff *skb, bool recalculate)
 {
         int err;
         u8 nexthdr;
         unsigned int off;
         unsigned int len;
         bool fragment;
         bool done;
         __sum16 *csum;
 
         fragment = false;
         done = false;
 
         off = sizeof(struct ipv6hdr);
 
         err = skb_maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN);
         if (err < 0)
                 goto out;
 
         nexthdr = ipv6_hdr(skb)->nexthdr;
 
         len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
         while (off <= len && !done) {
                 switch (nexthdr) {
                 case IPPROTO_DSTOPTS:
                 case IPPROTO_HOPOPTS:
                 case IPPROTO_ROUTING: {
                         struct ipv6_opt_hdr *hp;
 
                         err = skb_maybe_pull_tail(skb,
                                                   off +
                                                   sizeof(struct ipv6_opt_hdr),
                                                   MAX_IPV6_HDR_LEN);
                         if (err < 0)
                                 goto out;
 
                         hp = OPT_HDR(struct ipv6_opt_hdr, skb, off);
                         nexthdr = hp->nexthdr;
                         off += ipv6_optlen(hp);
                         break;
                 }
                 case IPPROTO_AH: {
                         struct ip_auth_hdr *hp;
 
                         err = skb_maybe_pull_tail(skb,
                                                   off +
                                                   sizeof(struct ip_auth_hdr),
                                                   MAX_IPV6_HDR_LEN);
                         if (err < 0)
                                 goto out;
 
                         hp = OPT_HDR(struct ip_auth_hdr, skb, off);
                         nexthdr = hp->nexthdr;
                         off += ipv6_authlen(hp);
                         break;
                 }
                 case IPPROTO_FRAGMENT: {
                         struct frag_hdr *hp;
 
                         err = skb_maybe_pull_tail(skb,
                                                   off +
                                                   sizeof(struct frag_hdr),
                                                   MAX_IPV6_HDR_LEN);
                         if (err < 0)
                                 goto out;
 
                         hp = OPT_HDR(struct frag_hdr, skb, off);
 
                         if (hp->frag_off & htons(IP6_OFFSET | IP6_MF))
                                 fragment = true;
 
                         nexthdr = hp->nexthdr;
                         off += sizeof(struct frag_hdr);
                         break;
                 }
                 default:
                         done = true;
                         break;
                 }
         }
 
         err = -EPROTO;
 
         if (!done || fragment)
                 goto out;
 
         csum = skb_checksum_setup_ip(skb, nexthdr, off);
         if (IS_ERR(csum))
                 return PTR_ERR(csum);
 
         if (recalculate)
                 *csum = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
                                          &ipv6_hdr(skb)->daddr,
                                          skb->len - off, nexthdr, 0);
         err = 0;
 
 out:
         return err;
 }
 
 /**
  * skb_checksum_setup - set up partial checksum offset
  * @skb: the skb to set up
  * @recalculate: if true the pseudo-header checksum will be recalculated
  */
 int skb_checksum_setup(struct sk_buff *skb, bool recalculate)
 {
         int err;
 
         switch (skb->protocol) {
         case htons(ETH_P_IP):
                 err = skb_checksum_setup_ipv4(skb, recalculate);
                 break;
 
         case htons(ETH_P_IPV6):
                 err = skb_checksum_setup_ipv6(skb, recalculate);
                 break;
 
         default:
                 err = -EPROTO;
                 break;
         }
 
         return err;
 }
 EXPORT_SYMBOL(skb_checksum_setup);
 
 /**
  * skb_checksum_maybe_trim - maybe trims the given skb
  * @skb: the skb to check
  * @transport_len: the data length beyond the network header
  *
  * Checks whether the given skb has data beyond the given transport length.
  * If so, returns a cloned skb trimmed to this transport length.
  * Otherwise returns the provided skb. Returns NULL in error cases
  * (e.g. transport_len exceeds skb length or out-of-memory).
  *
  * Caller needs to set the skb transport header and free any returned skb if it
  * differs from the provided skb.
  */
 static struct sk_buff *skb_checksum_maybe_trim(struct sk_buff *skb,
                                                unsigned int transport_len)
 {
         struct sk_buff *skb_chk;
         unsigned int len = skb_transport_offset(skb) + transport_len;
         int ret;
 
         if (skb->len < len)
                 return NULL;
         else if (skb->len == len)
                 return skb;
 
         skb_chk = skb_clone(skb, GFP_ATOMIC);
         if (!skb_chk)
                 return NULL;
 
         ret = pskb_trim_rcsum(skb_chk, len);
         if (ret) {
                 kfree_skb(skb_chk);
                 return NULL;
         }
 
         return skb_chk;
 }
 
 /**
  * skb_checksum_trimmed - validate checksum of an skb
  * @skb: the skb to check
  * @transport_len: the data length beyond the network header
  * @skb_chkf: checksum function to use
  *
  * Applies the given checksum function skb_chkf to the provided skb.
  * Returns a checked and maybe trimmed skb. Returns NULL on error.
  *
  * If the skb has data beyond the given transport length, then a
  * trimmed & cloned skb is checked and returned.
  *
  * Caller needs to set the skb transport header and free any returned skb if it
  * differs from the provided skb.
  */
 struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
                                      unsigned int transport_len,
                                      __sum16(*skb_chkf)(struct sk_buff *skb))
 {
         struct sk_buff *skb_chk;
         unsigned int offset = skb_transport_offset(skb);
         __sum16 ret;
 
         skb_chk = skb_checksum_maybe_trim(skb, transport_len);
         if (!skb_chk)
                 goto err;
 
         if (!pskb_may_pull(skb_chk, offset))
                 goto err;
 
         skb_pull_rcsum(skb_chk, offset);
         ret = skb_chkf(skb_chk);
         skb_push_rcsum(skb_chk, offset);
 
         if (ret)
                 goto err;
 
         return skb_chk;
 
 err:
         if (skb_chk && skb_chk != skb)
                 kfree_skb(skb_chk);
 
         return NULL;
 
 }
 EXPORT_SYMBOL(skb_checksum_trimmed);
 
 void __skb_warn_lro_forwarding(const struct sk_buff *skb)
 {
         net_warn_ratelimited("%s: received packets cannot be forwarded while LRO is enabled\n",
                              skb->dev->name);
 }
 EXPORT_SYMBOL(__skb_warn_lro_forwarding);
 
 void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)
 {
         if (head_stolen) {
                 skb_release_head_state(skb);
                 kmem_cache_free(net_hotdata.skbuff_cache, skb);
         } else {
                 __kfree_skb(skb);
         }
 }
 EXPORT_SYMBOL(kfree_skb_partial);
 
 /**
  * skb_try_coalesce - try to merge skb to prior one
  * @to: prior buffer
  * @from: buffer to add
  * @fragstolen: pointer to boolean
  * @delta_truesize: how much more was allocated than was requested
  */
 bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                       bool *fragstolen, int *delta_truesize)
 {
         struct skb_shared_info *to_shinfo, *from_shinfo;
         int i, delta, len = from->len;
 
         *fragstolen = false;
 
         if (skb_cloned(to))
                 return false;
 
         /* In general, avoid mixing page_pool and non-page_pool allocated
          * pages within the same SKB. In theory we could take full
          * references if @from is cloned and !@to->pp_recycle but its
          * tricky (due to potential race with the clone disappearing) and
          * rare, so not worth dealing with.
          */
         if (to->pp_recycle != from->pp_recycle)
                 return false;
 
         if (len <= skb_tailroom(to)) {
                 if (len)
                         BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));
                 *delta_truesize = 0;
                 return true;
         }
 
         to_shinfo = skb_shinfo(to);
         from_shinfo = skb_shinfo(from);
         if (to_shinfo->frag_list || from_shinfo->frag_list)
                 return false;
         if (skb_zcopy(to) || skb_zcopy(from))
                 return false;
 
         if (skb_headlen(from) != 0) {
                 struct page *page;
                 unsigned int offset;
 
                 if (to_shinfo->nr_frags +
                     from_shinfo->nr_frags >= MAX_SKB_FRAGS)
                         return false;
 
                 if (skb_head_is_locked(from))
                         return false;
 
                 delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));
 
                 page = virt_to_head_page(from->head);
                 offset = from->data - (unsigned char *)page_address(page);
 
                 skb_fill_page_desc(to, to_shinfo->nr_frags,
                                    page, offset, skb_headlen(from));
                 *fragstolen = true;
         } else {
                 if (to_shinfo->nr_frags +
                     from_shinfo->nr_frags > MAX_SKB_FRAGS)
                         return false;
 
                 delta = from->truesize - SKB_TRUESIZE(skb_end_offset(from));
         }
 
         WARN_ON_ONCE(delta < len);
 
         memcpy(to_shinfo->frags + to_shinfo->nr_frags,
                from_shinfo->frags,
                from_shinfo->nr_frags * sizeof(skb_frag_t));
         to_shinfo->nr_frags += from_shinfo->nr_frags;
 
         if (!skb_cloned(from))
                 from_shinfo->nr_frags = 0;
 
         /* if the skb is not cloned this does nothing
          * since we set nr_frags to 0.
          */
         if (skb_pp_frag_ref(from)) {
                 for (i = 0; i < from_shinfo->nr_frags; i++)
                         __skb_frag_ref(&from_shinfo->frags[i]);
         }
 
         to->truesize += delta;
         to->len += len;
         to->data_len += len;
 
         *delta_truesize = delta;
         return true;
 }
 EXPORT_SYMBOL(skb_try_coalesce);
 
 /**
  * skb_scrub_packet - scrub an skb
  *
  * @skb: buffer to clean
  * @xnet: packet is crossing netns
  *
  * skb_scrub_packet can be used after encapsulating or decapsulting a packet
  * into/from a tunnel. Some information have to be cleared during these
  * operations.
  * skb_scrub_packet can also be used to clean a skb before injecting it in
  * another namespace (@xnet == true). We have to clear all information in the
  * skb that could impact namespace isolation.
  */
 void skb_scrub_packet(struct sk_buff *skb, bool xnet)
 {
         skb->pkt_type = PACKET_HOST;
         skb->skb_iif = 0;
         skb->ignore_df = 0;
         skb_dst_drop(skb);
         skb_ext_reset(skb);
         nf_reset_ct(skb);
         nf_reset_trace(skb);
 
 #ifdef CONFIG_NET_SWITCHDEV
         skb->offload_fwd_mark = 0;
         skb->offload_l3_fwd_mark = 0;
 #endif
 
         if (!xnet)
                 return;
 
         ipvs_reset(skb);
         skb->mark = 0;
         skb_clear_tstamp(skb);
 }
 EXPORT_SYMBOL_GPL(skb_scrub_packet);
 
 static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
 {
         int mac_len, meta_len;
         void *meta;
 
         if (skb_cow(skb, skb_headroom(skb)) < 0) {
                 kfree_skb(skb);
                 return NULL;
         }
 
         mac_len = skb->data - skb_mac_header(skb);
         if (likely(mac_len > VLAN_HLEN + ETH_TLEN)) {
                 memmove(skb_mac_header(skb) + VLAN_HLEN, skb_mac_header(skb),
                         mac_len - VLAN_HLEN - ETH_TLEN);
         }
 
         meta_len = skb_metadata_len(skb);
         if (meta_len) {
                 meta = skb_metadata_end(skb) - meta_len;
                 memmove(meta + VLAN_HLEN, meta, meta_len);
         }
 
         skb->mac_header += VLAN_HLEN;
         return skb;
 }
 
 struct sk_buff *skb_vlan_untag(struct sk_buff *skb)
 {
         struct vlan_hdr *vhdr;
         u16 vlan_tci;
 
         if (unlikely(skb_vlan_tag_present(skb))) {
                 /* vlan_tci is already set-up so leave this for another time */
                 return skb;
         }
 
         skb = skb_share_check(skb, GFP_ATOMIC);
         if (unlikely(!skb))
                 goto err_free;
         /* We may access the two bytes after vlan_hdr in vlan_set_encap_proto(). */
         if (unlikely(!pskb_may_pull(skb, VLAN_HLEN + sizeof(unsigned short))))
                 goto err_free;
 
         vhdr = (struct vlan_hdr *)skb->data;
         vlan_tci = ntohs(vhdr->h_vlan_TCI);
         __vlan_hwaccel_put_tag(skb, skb->protocol, vlan_tci);
 
         skb_pull_rcsum(skb, VLAN_HLEN);
         vlan_set_encap_proto(skb, vhdr);
 
         skb = skb_reorder_vlan_header(skb);
         if (unlikely(!skb))
                 goto err_free;
 
         skb_reset_network_header(skb);
         if (!skb_transport_header_was_set(skb))
                 skb_reset_transport_header(skb);
         skb_reset_mac_len(skb);
 
         return skb;
 
 err_free:
         kfree_skb(skb);
         return NULL;
 }
 EXPORT_SYMBOL(skb_vlan_untag);
 
 int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len)
 {
         if (!pskb_may_pull(skb, write_len))
                 return -ENOMEM;
 
         if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
                 return 0;
 
         return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
 }
 EXPORT_SYMBOL(skb_ensure_writable);
 
 int skb_ensure_writable_head_tail(struct sk_buff *skb, struct net_device *dev)
 {
         int needed_headroom = dev->needed_headroom;
         int needed_tailroom = dev->needed_tailroom;
 
         /* For tail taggers, we need to pad short frames ourselves, to ensure
          * that the tail tag does not fail at its role of being at the end of
          * the packet, once the conduit interface pads the frame. Account for
          * that pad length here, and pad later.
          */
         if (unlikely(needed_tailroom && skb->len < ETH_ZLEN))
                 needed_tailroom += ETH_ZLEN - skb->len;
         /* skb_headroom() returns unsigned int... */
         needed_headroom = max_t(int, needed_headroom - skb_headroom(skb), 0);
         needed_tailroom = max_t(int, needed_tailroom - skb_tailroom(skb), 0);
 
         if (likely(!needed_headroom && !needed_tailroom && !skb_cloned(skb)))
                 /* No reallocation needed, yay! */
                 return 0;
 
         return pskb_expand_head(skb, needed_headroom, needed_tailroom,
                                 GFP_ATOMIC);
 }
 EXPORT_SYMBOL(skb_ensure_writable_head_tail);
 
 /* remove VLAN header from packet and update csum accordingly.
  * expects a non skb_vlan_tag_present skb with a vlan tag payload
  */
 int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
 {
         int offset = skb->data - skb_mac_header(skb);
         int err;
 
         if (WARN_ONCE(offset,
                       "__skb_vlan_pop got skb with skb->data not at mac header (offset %d)\n",
                       offset)) {
                 return -EINVAL;
         }
 
         err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
         if (unlikely(err))
                 return err;
 
         skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
 
         vlan_remove_tag(skb, vlan_tci);
 
         skb->mac_header += VLAN_HLEN;
 
         if (skb_network_offset(skb) < ETH_HLEN)
                 skb_set_network_header(skb, ETH_HLEN);
 
         skb_reset_mac_len(skb);
 
         return err;
 }
 EXPORT_SYMBOL(__skb_vlan_pop);
 
 /* Pop a vlan tag either from hwaccel or from payload.
  * Expects skb->data at mac header.
  */
 int skb_vlan_pop(struct sk_buff *skb)
 {
         u16 vlan_tci;
         __be16 vlan_proto;
         int err;
 
         if (likely(skb_vlan_tag_present(skb))) {
                 __vlan_hwaccel_clear_tag(skb);
         } else {
                 if (unlikely(!eth_type_vlan(skb->protocol)))
                         return 0;
 
                 err = __skb_vlan_pop(skb, &vlan_tci);
                 if (err)
                         return err;
         }
         /* move next vlan tag to hw accel tag */
         if (likely(!eth_type_vlan(skb->protocol)))
                 return 0;
 
         vlan_proto = skb->protocol;
         err = __skb_vlan_pop(skb, &vlan_tci);
         if (unlikely(err))
                 return err;
 
         __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
         return 0;
 }
 EXPORT_SYMBOL(skb_vlan_pop);
 
 /* Push a vlan tag either into hwaccel or into payload (if hwaccel tag present).
  * Expects skb->data at mac header.
  */
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
 {
         if (skb_vlan_tag_present(skb)) {
                 int offset = skb->data - skb_mac_header(skb);
                 int err;
 
                 if (WARN_ONCE(offset,
                               "skb_vlan_push got skb with skb->data not at mac header (offset %d)\n",
                               offset)) {
                         return -EINVAL;
                 }
 
                 err = __vlan_insert_tag(skb, skb->vlan_proto,
                                         skb_vlan_tag_get(skb));
                 if (err)
                         return err;
 
                 skb->protocol = skb->vlan_proto;
                 skb->mac_len += VLAN_HLEN;
 
                 skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
         }
         __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
         return 0;
 }
 EXPORT_SYMBOL(skb_vlan_push);
 
 /**
  * skb_eth_pop() - Drop the Ethernet header at the head of a packet
  *
  * @skb: Socket buffer to modify
  *
  * Drop the Ethernet header of @skb.
  *
  * Expects that skb->data points to the mac header and that no VLAN tags are
  * present.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_eth_pop(struct sk_buff *skb)
 {
         if (!pskb_may_pull(skb, ETH_HLEN) || skb_vlan_tagged(skb) ||
             skb_network_offset(skb) < ETH_HLEN)
                 return -EPROTO;
 
         skb_pull_rcsum(skb, ETH_HLEN);
         skb_reset_mac_header(skb);
         skb_reset_mac_len(skb);
 
         return 0;
 }
 EXPORT_SYMBOL(skb_eth_pop);
 
 /**
  * skb_eth_push() - Add a new Ethernet header at the head of a packet
  *
  * @skb: Socket buffer to modify
  * @dst: Destination MAC address of the new header
  * @src: Source MAC address of the new header
  *
  * Prepend @skb with a new Ethernet header.
  *
  * Expects that skb->data points to the mac header, which must be empty.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_eth_push(struct sk_buff *skb, const unsigned char *dst,
                  const unsigned char *src)
 {
         struct ethhdr *eth;
         int err;
 
         if (skb_network_offset(skb) || skb_vlan_tag_present(skb))
                 return -EPROTO;
 
         err = skb_cow_head(skb, sizeof(*eth));
         if (err < 0)
                 return err;
 
         skb_push(skb, sizeof(*eth));
         skb_reset_mac_header(skb);
         skb_reset_mac_len(skb);
 
         eth = eth_hdr(skb);
         ether_addr_copy(eth->h_dest, dst);
         ether_addr_copy(eth->h_source, src);
         eth->h_proto = skb->protocol;
 
         skb_postpush_rcsum(skb, eth, sizeof(*eth));
 
         return 0;
 }
 EXPORT_SYMBOL(skb_eth_push);
 
 /* Update the ethertype of hdr and the skb csum value if required. */
 static void skb_mod_eth_type(struct sk_buff *skb, struct ethhdr *hdr,
                              __be16 ethertype)
 {
         if (skb->ip_summed == CHECKSUM_COMPLETE) {
                 __be16 diff[] = { ~hdr->h_proto, ethertype };
 
                 skb->csum = csum_partial((char *)diff, sizeof(diff), skb->csum);
         }
 
         hdr->h_proto = ethertype;
 }
 
 /**
  * skb_mpls_push() - push a new MPLS header after mac_len bytes from start of
  *                   the packet
  *
  * @skb: buffer
  * @mpls_lse: MPLS label stack entry to push
  * @mpls_proto: ethertype of the new MPLS header (expects 0x8847 or 0x8848)
  * @mac_len: length of the MAC header
  * @ethernet: flag to indicate if the resulting packet after skb_mpls_push is
  *            ethernet
  *
  * Expects skb->data at mac header.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
                   int mac_len, bool ethernet)
 {
         struct mpls_shim_hdr *lse;
         int err;
 
         if (unlikely(!eth_p_mpls(mpls_proto)))
                 return -EINVAL;
 
         /* Networking stack does not allow simultaneous Tunnel and MPLS GSO. */
         if (skb->encapsulation)
                 return -EINVAL;
 
         err = skb_cow_head(skb, MPLS_HLEN);
         if (unlikely(err))
                 return err;
 
         if (!skb->inner_protocol) {
                 skb_set_inner_network_header(skb, skb_network_offset(skb));
                 skb_set_inner_protocol(skb, skb->protocol);
         }
 
         skb_push(skb, MPLS_HLEN);
         memmove(skb_mac_header(skb) - MPLS_HLEN, skb_mac_header(skb),
                 mac_len);
         skb_reset_mac_header(skb);
         skb_set_network_header(skb, mac_len);
         skb_reset_mac_len(skb);
 
         lse = mpls_hdr(skb);
         lse->label_stack_entry = mpls_lse;
         skb_postpush_rcsum(skb, lse, MPLS_HLEN);
 
         if (ethernet && mac_len >= ETH_HLEN)
                 skb_mod_eth_type(skb, eth_hdr(skb), mpls_proto);
         skb->protocol = mpls_proto;
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_mpls_push);
 
 /**
  * skb_mpls_pop() - pop the outermost MPLS header
  *
  * @skb: buffer
  * @next_proto: ethertype of header after popped MPLS header
  * @mac_len: length of the MAC header
  * @ethernet: flag to indicate if the packet is ethernet
  *
  * Expects skb->data at mac header.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
                  bool ethernet)
 {
         int err;
 
         if (unlikely(!eth_p_mpls(skb->protocol)))
                 return 0;
 
         err = skb_ensure_writable(skb, mac_len + MPLS_HLEN);
         if (unlikely(err))
                 return err;
 
         skb_postpull_rcsum(skb, mpls_hdr(skb), MPLS_HLEN);
         memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),
                 mac_len);
 
         __skb_pull(skb, MPLS_HLEN);
         skb_reset_mac_header(skb);
         skb_set_network_header(skb, mac_len);
 
         if (ethernet && mac_len >= ETH_HLEN) {
                 struct ethhdr *hdr;
 
                 /* use mpls_hdr() to get ethertype to account for VLANs. */
                 hdr = (struct ethhdr *)((void *)mpls_hdr(skb) - ETH_HLEN);
                 skb_mod_eth_type(skb, hdr, next_proto);
         }
         skb->protocol = next_proto;
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_mpls_pop);
 
 /**
  * skb_mpls_update_lse() - modify outermost MPLS header and update csum
  *
  * @skb: buffer
  * @mpls_lse: new MPLS label stack entry to update to
  *
  * Expects skb->data at mac header.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse)
 {
         int err;
 
         if (unlikely(!eth_p_mpls(skb->protocol)))
                 return -EINVAL;
 
         err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
         if (unlikely(err))
                 return err;
 
         if (skb->ip_summed == CHECKSUM_COMPLETE) {
                 __be32 diff[] = { ~mpls_hdr(skb)->label_stack_entry, mpls_lse };
 
                 skb->csum = csum_partial((char *)diff, sizeof(diff), skb->csum);
         }
 
         mpls_hdr(skb)->label_stack_entry = mpls_lse;
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(skb_mpls_update_lse);
 
 /**
  * skb_mpls_dec_ttl() - decrement the TTL of the outermost MPLS header
  *
  * @skb: buffer
  *
  * Expects skb->data at mac header.
  *
  * Returns 0 on success, -errno otherwise.
  */
 int skb_mpls_dec_ttl(struct sk_buff *skb)
 {
         u32 lse;
         u8 ttl;
 
         if (unlikely(!eth_p_mpls(skb->protocol)))
                 return -EINVAL;
 
         if (!pskb_may_pull(skb, skb_network_offset(skb) + MPLS_HLEN))
                 return -ENOMEM;
 
         lse = be32_to_cpu(mpls_hdr(skb)->label_stack_entry);
         ttl = (lse & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
         if (!--ttl)
                 return -EINVAL;
 
         lse &= ~MPLS_LS_TTL_MASK;
         lse |= ttl << MPLS_LS_TTL_SHIFT;
 
         return skb_mpls_update_lse(skb, cpu_to_be32(lse));
 }
 EXPORT_SYMBOL_GPL(skb_mpls_dec_ttl);
 
 /**
  * alloc_skb_with_frags - allocate skb with page frags
  *
  * @header_len: size of linear part
  * @data_len: needed length in frags
  * @order: max page order desired.
  * @errcode: pointer to error code if any
  * @gfp_mask: allocation mask
  *
  * This can be used to allocate a paged skb, given a maximal order for frags.
  */
 struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
                                      unsigned long data_len,
                                      int order,
                                      int *errcode,
                                      gfp_t gfp_mask)
 {
         unsigned long chunk;
         struct sk_buff *skb;
         struct page *page;
         int nr_frags = 0;
 
         *errcode = -EMSGSIZE;
         if (unlikely(data_len > MAX_SKB_FRAGS * (PAGE_SIZE << order)))
                 return NULL;
 
         *errcode = -ENOBUFS;
         skb = alloc_skb(header_len, gfp_mask);
         if (!skb)
                 return NULL;
 
         while (data_len) {
                 if (nr_frags == MAX_SKB_FRAGS - 1)
                         goto failure;
                 while (order && PAGE_ALIGN(data_len) < (PAGE_SIZE << order))
                         order--;
 
                 if (order) {
                         page = alloc_pages((gfp_mask & ~__GFP_DIRECT_RECLAIM) |
                                            __GFP_COMP |
                                            __GFP_NOWARN,
                                            order);
                         if (!page) {
                                 order--;
                                 continue;
                         }
                 } else {
                         page = alloc_page(gfp_mask);
                         if (!page)
                                 goto failure;
                 }
                 chunk = min_t(unsigned long, data_len,
                               PAGE_SIZE << order);
                 skb_fill_page_desc(skb, nr_frags, page, 0, chunk);
                 nr_frags++;
                 skb->truesize += (PAGE_SIZE << order);
                 data_len -= chunk;
         }
         return skb;
 
 failure:
         kfree_skb(skb);
         return NULL;
 }
 EXPORT_SYMBOL(alloc_skb_with_frags);
 
 /* carve out the first off bytes from skb when off < headlen */
 static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
                                     const int headlen, gfp_t gfp_mask)
 {
         int i;
         unsigned int size = skb_end_offset(skb);
         int new_hlen = headlen - off;
         u8 *data;
 
         if (skb_pfmemalloc(skb))
                 gfp_mask |= __GFP_MEMALLOC;
 
         data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
         if (!data)
                 return -ENOMEM;
         size = SKB_WITH_OVERHEAD(size);
 
         /* Copy real data, and all frags */
         skb_copy_from_linear_data_offset(skb, off, data, new_hlen);
         skb->len -= off;
 
         memcpy((struct skb_shared_info *)(data + size),
                skb_shinfo(skb),
                offsetof(struct skb_shared_info,
                         frags[skb_shinfo(skb)->nr_frags]));
         if (skb_cloned(skb)) {
                 /* drop the old head gracefully */
                 if (skb_orphan_frags(skb, gfp_mask)) {
                         skb_kfree_head(data, size);
                         return -ENOMEM;
                 }
                 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                         skb_frag_ref(skb, i);
                 if (skb_has_frag_list(skb))
                         skb_clone_fraglist(skb);
                 skb_release_data(skb, SKB_CONSUMED);
         } else {
                 /* we can reuse existing recount- all we did was
                  * relocate values
                  */
                 skb_free_head(skb);
         }
 
         skb->head = data;
         skb->data = data;
         skb->head_frag = 0;
         skb_set_end_offset(skb, size);
         skb_set_tail_pointer(skb, skb_headlen(skb));
         skb_headers_offset_update(skb, 0);
         skb->cloned = 0;
         skb->hdr_len = 0;
         skb->nohdr = 0;
         atomic_set(&skb_shinfo(skb)->dataref, 1);
 
         return 0;
 }
 
 static int pskb_carve(struct sk_buff *skb, const u32 off, gfp_t gfp);
 
 /* carve out the first eat bytes from skb's frag_list. May recurse into
  * pskb_carve()
  */
 static int pskb_carve_frag_list(struct sk_buff *skb,
                                 struct skb_shared_info *shinfo, int eat,
                                 gfp_t gfp_mask)
 {
         struct sk_buff *list = shinfo->frag_list;
         struct sk_buff *clone = NULL;
         struct sk_buff *insp = NULL;
 
         do {
                 if (!list) {
                         pr_err("Not enough bytes to eat. Want %d\n", eat);
                         return -EFAULT;
                 }
                 if (list->len <= eat) {
                         /* Eaten as whole. */
                         eat -= list->len;
                         list = list->next;
                         insp = list;
                 } else {
                         /* Eaten partially. */
                         if (skb_shared(list)) {
                                 clone = skb_clone(list, gfp_mask);
                                 if (!clone)
                                         return -ENOMEM;
                                 insp = list->next;
                                 list = clone;
                         } else {
                                 /* This may be pulled without problems. */
                                 insp = list;
                         }
                         if (pskb_carve(list, eat, gfp_mask) < 0) {
                                 kfree_skb(clone);
                                 return -ENOMEM;
                         }
                         break;
                 }
         } while (eat);
 
         /* Free pulled out fragments. */
         while ((list = shinfo->frag_list) != insp) {
                 shinfo->frag_list = list->next;
                 consume_skb(list);
         }
         /* And insert new clone at head. */
         if (clone) {
                 clone->next = list;
                 shinfo->frag_list = clone;
         }
         return 0;
 }
 
 /* carve off first len bytes from skb. Split line (off) is in the
  * non-linear part of skb
  */
 static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
                                        int pos, gfp_t gfp_mask)
 {
         int i, k = 0;
         unsigned int size = skb_end_offset(skb);
         u8 *data;
         const int nfrags = skb_shinfo(skb)->nr_frags;
         struct skb_shared_info *shinfo;
 
         if (skb_pfmemalloc(skb))
                 gfp_mask |= __GFP_MEMALLOC;
 
         data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
         if (!data)
                 return -ENOMEM;
         size = SKB_WITH_OVERHEAD(size);
 
         memcpy((struct skb_shared_info *)(data + size),
                skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));
         if (skb_orphan_frags(skb, gfp_mask)) {
                 skb_kfree_head(data, size);
                 return -ENOMEM;
         }
         shinfo = (struct skb_shared_info *)(data + size);
         for (i = 0; i < nfrags; i++) {
                 int fsize = skb_frag_size(&skb_shinfo(skb)->frags[i]);
 
                 if (pos + fsize > off) {
                         shinfo->frags[k] = skb_shinfo(skb)->frags[i];
 
                         if (pos < off) {
                                 /* Split frag.
                                  * We have two variants in this case:
                                  * 1. Move all the frag to the second
                                  *    part, if it is possible. F.e.
                                  *    this approach is mandatory for TUX,
                                  *    where splitting is expensive.
                                  * 2. Split is accurately. We make this.
                                  */
                                 skb_frag_off_add(&shinfo->frags[0], off - pos);
                                 skb_frag_size_sub(&shinfo->frags[0], off - pos);
                         }
                         skb_frag_ref(skb, i);
                         k++;
                 }
                 pos += fsize;
         }
         shinfo->nr_frags = k;
         if (skb_has_frag_list(skb))
                 skb_clone_fraglist(skb);
 
         /* split line is in frag list */
         if (k == 0 && pskb_carve_frag_list(skb, shinfo, off - pos, gfp_mask)) {
                 /* skb_frag_unref() is not needed here as shinfo->nr_frags = 0. */
                 if (skb_has_frag_list(skb))
                         kfree_skb_list(skb_shinfo(skb)->frag_list);
                 skb_kfree_head(data, size);
                 return -ENOMEM;
         }
         skb_release_data(skb, SKB_CONSUMED);
 
         skb->head = data;
         skb->head_frag = 0;
         skb->data = data;
         skb_set_end_offset(skb, size);
         skb_reset_tail_pointer(skb);
         skb_headers_offset_update(skb, 0);
         skb->cloned   = 0;
         skb->hdr_len  = 0;
         skb->nohdr    = 0;
         skb->len -= off;
         skb->data_len = skb->len;
         atomic_set(&skb_shinfo(skb)->dataref, 1);
         return 0;
 }
 
 /* remove len bytes from the beginning of the skb */
 static int pskb_carve(struct sk_buff *skb, const u32 len, gfp_t gfp)
 {
         int headlen = skb_headlen(skb);
 
         if (len < headlen)
                 return pskb_carve_inside_header(skb, len, headlen, gfp);
         else
                 return pskb_carve_inside_nonlinear(skb, len, headlen, gfp);
 }
 
 /* Extract to_copy bytes starting at off from skb, and return this in
  * a new skb
  */
 struct sk_buff *pskb_extract(struct sk_buff *skb, int off,
                              int to_copy, gfp_t gfp)
 {
         struct sk_buff  *clone = skb_clone(skb, gfp);
 
         if (!clone)
                 return NULL;
 
         if (pskb_carve(clone, off, gfp) < 0 ||
             pskb_trim(clone, to_copy)) {
                 kfree_skb(clone);
                 return NULL;
         }
         return clone;
 }
 EXPORT_SYMBOL(pskb_extract);
 
 /**
  * skb_condense - try to get rid of fragments/frag_list if possible
  * @skb: buffer
  *
  * Can be used to save memory before skb is added to a busy queue.
  * If packet has bytes in frags and enough tail room in skb->head,
  * pull all of them, so that we can free the frags right now and adjust
  * truesize.
  * Notes:
  *      We do not reallocate skb->head thus can not fail.
  *      Caller must re-evaluate skb->truesize if needed.
  */
 void skb_condense(struct sk_buff *skb)
 {
         if (skb->data_len) {
                 if (skb->data_len > skb->end - skb->tail ||
                     skb_cloned(skb))
                         return;
 
                 /* Nice, we can free page frag(s) right now */
                 __pskb_pull_tail(skb, skb->data_len);
         }
         /* At this point, skb->truesize might be over estimated,
          * because skb had a fragment, and fragments do not tell
          * their truesize.
          * When we pulled its content into skb->head, fragment
          * was freed, but __pskb_pull_tail() could not possibly
          * adjust skb->truesize, not knowing the frag truesize.
          */
         skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
 }
 EXPORT_SYMBOL(skb_condense);
 
 #ifdef CONFIG_SKB_EXTENSIONS
 static void *skb_ext_get_ptr(struct skb_ext *ext, enum skb_ext_id id)
 {
         return (void *)ext + (ext->offset[id] * SKB_EXT_ALIGN_VALUE);
 }
 
 /**
  * __skb_ext_alloc - allocate a new skb extensions storage
  *
  * @flags: See kmalloc().
  *
  * Returns the newly allocated pointer. The pointer can later attached to a
  * skb via __skb_ext_set().
  * Note: caller must handle the skb_ext as an opaque data.
  */
 struct skb_ext *__skb_ext_alloc(gfp_t flags)
 {
         struct skb_ext *new = kmem_cache_alloc(skbuff_ext_cache, flags);
 
         if (new) {
                 memset(new->offset, 0, sizeof(new->offset));
                 refcount_set(&new->refcnt, 1);
         }
 
         return new;
 }
 
 static struct skb_ext *skb_ext_maybe_cow(struct skb_ext *old,
                                          unsigned int old_active)
 {
         struct skb_ext *new;
 
         if (refcount_read(&old->refcnt) == 1)
                 return old;
 
         new = kmem_cache_alloc(skbuff_ext_cache, GFP_ATOMIC);
         if (!new)
                 return NULL;
 
         memcpy(new, old, old->chunks * SKB_EXT_ALIGN_VALUE);
         refcount_set(&new->refcnt, 1);
 
 #ifdef CONFIG_XFRM
         if (old_active & (1 << SKB_EXT_SEC_PATH)) {
                 struct sec_path *sp = skb_ext_get_ptr(old, SKB_EXT_SEC_PATH);
                 unsigned int i;
 
                 for (i = 0; i < sp->len; i++)
                         xfrm_state_hold(sp->xvec[i]);
         }
 #endif
 #ifdef CONFIG_MCTP_FLOWS
         if (old_active & (1 << SKB_EXT_MCTP)) {
                 struct mctp_flow *flow = skb_ext_get_ptr(old, SKB_EXT_MCTP);
 
                 if (flow->key)
                         refcount_inc(&flow->key->refs);
         }
 #endif
         __skb_ext_put(old);
         return new;
 }
 
 /**
  * __skb_ext_set - attach the specified extension storage to this skb
  * @skb: buffer
  * @id: extension id
  * @ext: extension storage previously allocated via __skb_ext_alloc()
  *
  * Existing extensions, if any, are cleared.
  *
  * Returns the pointer to the extension.
  */
 void *__skb_ext_set(struct sk_buff *skb, enum skb_ext_id id,
                     struct skb_ext *ext)
 {
         unsigned int newlen, newoff = SKB_EXT_CHUNKSIZEOF(*ext);
 
         skb_ext_put(skb);
         newlen = newoff + skb_ext_type_len[id];
         ext->chunks = newlen;
         ext->offset[id] = newoff;
         skb->extensions = ext;
         skb->active_extensions = 1 << id;
         return skb_ext_get_ptr(ext, id);
 }
 
 /**
  * skb_ext_add - allocate space for given extension, COW if needed
  * @skb: buffer
  * @id: extension to allocate space for
  *
  * Allocates enough space for the given extension.
  * If the extension is already present, a pointer to that extension
  * is returned.
  *
  * If the skb was cloned, COW applies and the returned memory can be
  * modified without changing the extension space of clones buffers.
  *
  * Returns pointer to the extension or NULL on allocation failure.
  */
 void *skb_ext_add(struct sk_buff *skb, enum skb_ext_id id)
 {
         struct skb_ext *new, *old = NULL;
         unsigned int newlen, newoff;
 
         if (skb->active_extensions) {
                 old = skb->extensions;
 
                 new = skb_ext_maybe_cow(old, skb->active_extensions);
                 if (!new)
                         return NULL;
 
                 if (__skb_ext_exist(new, id))
                         goto set_active;
 
                 newoff = new->chunks;
         } else {
                 newoff = SKB_EXT_CHUNKSIZEOF(*new);
 
                 new = __skb_ext_alloc(GFP_ATOMIC);
                 if (!new)
                         return NULL;
         }
 
         newlen = newoff + skb_ext_type_len[id];
         new->chunks = newlen;
         new->offset[id] = newoff;
 set_active:
         skb->slow_gro = 1;
         skb->extensions = new;
         skb->active_extensions |= 1 << id;
         return skb_ext_get_ptr(new, id);
 }
 EXPORT_SYMBOL(skb_ext_add);
 
 #ifdef CONFIG_XFRM
 static void skb_ext_put_sp(struct sec_path *sp)
 {
         unsigned int i;
 
         for (i = 0; i < sp->len; i++)
                 xfrm_state_put(sp->xvec[i]);
 }
 #endif
 
 #ifdef CONFIG_MCTP_FLOWS
 static void skb_ext_put_mctp(struct mctp_flow *flow)
 {
         if (flow->key)
                 mctp_key_unref(flow->key);
 }
 #endif
 
 void __skb_ext_del(struct sk_buff *skb, enum skb_ext_id id)
 {
         struct skb_ext *ext = skb->extensions;
 
         skb->active_extensions &= ~(1 << id);
         if (skb->active_extensions == 0) {
                 skb->extensions = NULL;
                 __skb_ext_put(ext);
 #ifdef CONFIG_XFRM
         } else if (id == SKB_EXT_SEC_PATH &&
                    refcount_read(&ext->refcnt) == 1) {
                 struct sec_path *sp = skb_ext_get_ptr(ext, SKB_EXT_SEC_PATH);
 
                 skb_ext_put_sp(sp);
                 sp->len = 0;
 #endif
         }
 }
 EXPORT_SYMBOL(__skb_ext_del);
 
 void __skb_ext_put(struct skb_ext *ext)
 {
         /* If this is last clone, nothing can increment
          * it after check passes.  Avoids one atomic op.
          */
         if (refcount_read(&ext->refcnt) == 1)
                 goto free_now;
 
         if (!refcount_dec_and_test(&ext->refcnt))
                 return;
 free_now:
 #ifdef CONFIG_XFRM
         if (__skb_ext_exist(ext, SKB_EXT_SEC_PATH))
                 skb_ext_put_sp(skb_ext_get_ptr(ext, SKB_EXT_SEC_PATH));
 #endif
 #ifdef CONFIG_MCTP_FLOWS
         if (__skb_ext_exist(ext, SKB_EXT_MCTP))
                 skb_ext_put_mctp(skb_ext_get_ptr(ext, SKB_EXT_MCTP));
 #endif
 
         kmem_cache_free(skbuff_ext_cache, ext);
 }
 EXPORT_SYMBOL(__skb_ext_put);
 #endif /* CONFIG_SKB_EXTENSIONS */
 
 static void kfree_skb_napi_cache(struct sk_buff *skb)
 {
         /* if SKB is a clone, don't handle this case */
         if (skb->fclone != SKB_FCLONE_UNAVAILABLE) {
                 __kfree_skb(skb);
                 return;
         }
 
         local_bh_disable();
         __napi_kfree_skb(skb, SKB_CONSUMED);
         local_bh_enable();
 }
 
 /**
  * skb_attempt_defer_free - queue skb for remote freeing
  * @skb: buffer
  *
  * Put @skb in a per-cpu list, using the cpu which
  * allocated the skb/pages to reduce false sharing
  * and memory zone spinlock contention.
  */
 void skb_attempt_defer_free(struct sk_buff *skb)
 {
         int cpu = skb->alloc_cpu;
         struct softnet_data *sd;
         unsigned int defer_max;
         bool kick;
 
         if (cpu == raw_smp_processor_id() ||
             WARN_ON_ONCE(cpu >= nr_cpu_ids) ||
             !cpu_online(cpu)) {
 nodefer:        kfree_skb_napi_cache(skb);
                 return;
         }
 
         DEBUG_NET_WARN_ON_ONCE(skb_dst(skb));
         DEBUG_NET_WARN_ON_ONCE(skb->destructor);
 
         sd = &per_cpu(softnet_data, cpu);
         defer_max = READ_ONCE(net_hotdata.sysctl_skb_defer_max);
         if (READ_ONCE(sd->defer_count) >= defer_max)
                 goto nodefer;
 
         spin_lock_bh(&sd->defer_lock);
         /* Send an IPI every time queue reaches half capacity. */
         kick = sd->defer_count == (defer_max >> 1);
         /* Paired with the READ_ONCE() few lines above */
         WRITE_ONCE(sd->defer_count, sd->defer_count + 1);
 
         skb->next = sd->defer_list;
         /* Paired with READ_ONCE() in skb_defer_free_flush() */
         WRITE_ONCE(sd->defer_list, skb);
         spin_unlock_bh(&sd->defer_lock);
 
         /* Make sure to trigger NET_RX_SOFTIRQ on the remote CPU
          * if we are unlucky enough (this seems very unlikely).
          */
         if (unlikely(kick))
                 kick_defer_list_purge(sd, cpu);
 }
 
 static void skb_splice_csum_page(struct sk_buff *skb, struct page *page,
                                  size_t offset, size_t len)
 {
         const char *kaddr;
         __wsum csum;
 
         kaddr = kmap_local_page(page);
         csum = csum_partial(kaddr + offset, len, 0);
         kunmap_local(kaddr);
         skb->csum = csum_block_add(skb->csum, csum, skb->len);
 }
 
 /**
  * skb_splice_from_iter - Splice (or copy) pages to skbuff
  * @skb: The buffer to add pages to
  * @iter: Iterator representing the pages to be added
  * @maxsize: Maximum amount of pages to be added
  * @gfp: Allocation flags
  *
  * This is a common helper function for supporting MSG_SPLICE_PAGES.  It
  * extracts pages from an iterator and adds them to the socket buffer if
  * possible, copying them to fragments if not possible (such as if they're slab
  * pages).
  *
  * Returns the amount of data spliced/copied or -EMSGSIZE if there's
  * insufficient space in the buffer to transfer anything.
  */
 ssize_t skb_splice_from_iter(struct sk_buff *skb, struct iov_iter *iter,
                              ssize_t maxsize, gfp_t gfp)
 {
         size_t frag_limit = READ_ONCE(net_hotdata.sysctl_max_skb_frags);
         struct page *pages[8], **ppages = pages;
         ssize_t spliced = 0, ret = 0;
         unsigned int i;
 
         while (iter->count > 0) {
                 ssize_t space, nr, len;
                 size_t off;
 
                 ret = -EMSGSIZE;
                 space = frag_limit - skb_shinfo(skb)->nr_frags;
                 if (space < 0)
                         break;
 
                 /* We might be able to coalesce without increasing nr_frags */
                 nr = clamp_t(size_t, space, 1, ARRAY_SIZE(pages));
 
                 len = iov_iter_extract_pages(iter, &ppages, maxsize, nr, 0, &off);
                 if (len <= 0) {
                         ret = len ?: -EIO;
                         break;
                 }
 
                 i = 0;
                 do {
                         struct page *page = pages[i++];
                         size_t part = min_t(size_t, PAGE_SIZE - off, len);
 
                         ret = -EIO;
                         if (WARN_ON_ONCE(!sendpage_ok(page)))
                                 goto out;
 
                         ret = skb_append_pagefrags(skb, page, off, part,
                                                    frag_limit);
                         if (ret < 0) {
                                 iov_iter_revert(iter, len);
                                 goto out;
                         }
 
                         if (skb->ip_summed == CHECKSUM_NONE)
                                 skb_splice_csum_page(skb, page, off, part);
 
                         off = 0;
                         spliced += part;
                         maxsize -= part;
                         len -= part;
                 } while (len > 0);
 
                 if (maxsize <= 0)
                         break;
         }
 
 out:
         skb_len_add(skb, spliced);
         return spliced ?: ret;
 }
 EXPORT_SYMBOL(skb_splice_from_iter);
 
 static __always_inline
 size_t memcpy_from_iter_csum(void *iter_from, size_t progress,
                              size_t len, void *to, void *priv2)
 {
         __wsum *csum = priv2;
         __wsum next = csum_partial_copy_nocheck(iter_from, to + progress, len);
 
         *csum = csum_block_add(*csum, next, progress);
         return 0;
 }
 
 static __always_inline
 size_t copy_from_user_iter_csum(void __user *iter_from, size_t progress,
                                 size_t len, void *to, void *priv2)
 {
         __wsum next, *csum = priv2;
 
         next = csum_and_copy_from_user(iter_from, to + progress, len);
         *csum = csum_block_add(*csum, next, progress);
         return next ? 0 : len;
 }
 
 bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
                                   __wsum *csum, struct iov_iter *i)
 {
         size_t copied;
 
         if (WARN_ON_ONCE(!i->data_source))
                 return false;
         copied = iterate_and_advance2(i, bytes, addr, csum,
                                       copy_from_user_iter_csum,
                                       memcpy_from_iter_csum);
         if (likely(copied == bytes))
                 return true;
         iov_iter_revert(i, copied);
         return false;
 }
 EXPORT_SYMBOL(csum_and_copy_from_iter_full);